I think it's fair to say that most of us would say yes. However the reality is that a pure yellow mixed equally with a pure blue will make black or gray. So when we say that yellow and blue makes green we are not talking about pure colors. This may seem a bit pedantic, but if we start off with a false notion, then our attempts to mix color won't be too successful.
One of the recurring complaints of painters (and not just beginners!) is that their colors lose their vibrancy and turn muddy; this happens a lot in watercolors where paints mix into each other, or when paint is applied in layers. The colors that are mixed effectively cancel each other out: so instead of making a beautiful green, the vibrant blue and yellow ends up as a muddy brown.
Other colors like green and red mixed together do the same thing.
But ... if we mix yellow with a greenish blue, we get a brilliant green.
So what's happening?
To understand why some paints will mix well and others not, we need to know a bit about color theory, which is the purpose of this article. But as it's a bit technical, what I've done is to summarise the key points at the end of each section. If you prefer to skip all of the technical stuff then you can jump straight to A Correct Color Wheel
But before continuing it would be reasonable to ask if any of this is relevant to painting digitally? Well yes, it is, because when we paint in Photoshop it's just the same as painting on paper. If we try to put one color over an opposing color (say red over green) then we will get mud, just like we do with paint and paper.
Pure Blue and pure Yellow, mixed in equal proportions, makes gray or black ... and red and green also makes gray or black.
If we look at a simplified spectrum of visible light, this is what we see: Red, Green and Blue.
Of course the spectrum is more complex as there is also orange and yellow between the red and green, and cyan between the green and yellow. But for the purposes of this discussion these three primaries are enough and we can think of white light as being made up of an equal mix of red, green and blue light.
When we apply paint, say red paint, to paper, what happens is that the paint absorbs the blue and green light and reflects the red light (which is why we see a red color, of course).
Imagine that a strip of red paint has been painted and red, green and blue light is shone onto the strip, with screens to stop the lights from overlapping. Well what we'll see then is black where the red paint has absorbed the blue and green lights, and red where the red paint has reflected the red light.
And in this image, imagine that three strips of paint have been applied: red at the top, green in the middle and blue at the bottom; and again we shine red, green and blue light on these strips, as we did above.
Well the red strip will only reflect the red light, the green strip will only reflect the green light, and the blue strip will only reflect the blue light.
As it happens, we have three color receptors in our eyes: red, green and blue, so we can see these colors directly. Other colors require some processing in the brain: so when we see both red and green light at the same time, our eyes interpret this as yellow, which is a bit strange, but true; when we see green and blue at the same time, we interpret this as cyan; and, rather surprisingly, when we 'see' red and blue at the same time we interpret this as magenta (what makes this even more remarkable is that magenta is a color that doesn't actually exist in the visible spectrum, it's a construct of our brains).
So there are two things that are happening: on the paper some of the colors in the spectrum get absorbed by the paint and others get reflected by the paint; and in our eyes and brain the reflected light gets processed to give us the experience of red, green, yellow, orange etc. (In reality, all colors are constructs of our brain: outside of our minds there are only different electromagnetic frequencies and other animals see colors that we don't, and don't see colors that we do).
Now what happens when we mix red and green paint, say, apply it to the paper, and shine white light onto it?
Well, since the red paint will absorb the blue and green; and the green will absorb the red and blue ... we are left with all the colors absorbed. So we end up with no light reflected, or black.
In this image I've separated out the red and green paints onto two strips with our usual red, green and blue spotlights. Blue will be absorbed by both the red and green paints so we see no blue reflected. Now, if you imagine that these strips are combined into one, with red/green paint applied, then the green will disappear because it will be absorbed by the red paint, and the red will disappear because it will be absorbed by the green paint.
I've shown this in the blob at the right where I've applied green paint over red paint (or vice-versa, it doesn't matter) and you can see that the result is black. Of course, in practise with paint on paper, some light will always be reflected, so we will see some shade of gray rather than black.
For the same reasons, mixing blue and green paint or blue and red paint does the same: we end up with gray or black.
And, of course, if we mix all three colors, red, green and blue then we definitely end up with gray or black.
Mixing red, green and blue paint in any combination (or all three together) will give us gray or black.
So you can see that red, green and blue paints by themselves are not much use to us! Which makes one wonder why artists almost always say that yellow, blue and red are the three primary colors and that with these we can get all the colors that we need, sort of at any rate. Is there something special about yellow?
Well not really. Yellow, red and blue do not make good primary colors: mixing red and blue will give gray, and yellow and blue will also give gray; so it comes as a bit of a relief to find that red and yellow will give an orange! Still, yellow, red, blue and orange isn't a whole lot better than red, green and blue.
I can hear screams: 'But I KNOW that I get purple if I mix red and blue!!'. Yes, red and blue will give a sort of purple, providing the paints are not fully saturated (in watercolors, providing the paints are dilute so that the paper white shows through).
I've taken a 50% diluted blue paint and put it on top of a 50% diluted red paint. What happens is that the blue paint absorbs only 50% of the red and green light and the red paint absorbs only 50% of the green and blue light: so all of the green is absorbed but 50% of the red and blue are reflected. Because the eye interprets red+blue to be magenta, this is what we see: an undersaturated magenta, or purple.
We won't get good colors by mixing Red, Green and Blue paints; and we also won't get good colors by mixing Red, Blue and Yellow paints. The traditional artist's color wheel which uses Yellow, Red and Blue as the primary colors is confusing, at best.
The problem with Red, Green and Blue, in particular, is that they don't overlap each other on the spectrum: so, in theory at any rate, any combination of the three results in all the light in the spectrum being absorbed. In practise we can get some secondary colors from them (if the red, green and blue paints are not fully saturated or if there is more of one color than the other) but they won't be very good colors. Yellow, Red and Blue is a slightly better combination, but mainly because we can't get yellow from Red, Green and Blue whereas we can get a green of sorts from Yellow and Blue.
So we need three or more colors that do overlap each other: then when we mix them together, they won't absorb all of the light.
Yellow, Magenta and Cyan fit the bill perfectly, because Cyan reflects blue and green light; Magenta reflects blue and red light; and Yellow reflects red and green light. So combining any of these two colors will allow one of the Red, Green or Blue colors to be reflected. And combining all three colors will block all light, so we get black.
We can also think of Cyan as NOT Red (since it absorbs red and reflects blue and green), Magenta as NOT Green, and Yellow as NOT Blue. We can show this both mathematically and visually: if we take the Red/Green/Blue spectrum we started off with and invert it, this is exactly what we get: Cyan, Magenta and Yellow.
As I show underneath the Cyan/Magenta/Yellow spectrum, if we mix yellow and magenta we get red; if we mix cyan and yellow we get green; and if we mix magenta and cyan we get blue.
So with these three colors we can get all six colors ... and they are fully saturated, not muddy and grayish ... well, at least not in theory.
Cyan, Magenta and Yellow are the correct primaries for painting ... NOT Red, Green and Blue ... and NOT Yellow, Blue and Red.
We need to remember that Cyan is the result of red light being absorbed by the paint and Magenta is the result of green light being absorbed by the paint. So if both red and green have been absorbed by the two paints mixed together, blue light will still be reflected by the paint, and so a mixture of Cyan and Magenta gives us blue.
Exactly the same happens when we mix Cyan and Yellow to get green and Magenta and Yellow to get red.
Cyan + Yellow makes Green; Cyan + Magenta makes Blue; Yellow + Magenta makes Red.
In Photoshop yes, because in Photoshop we can use pure colors; in traditional painting no, because paints are never pure and are always a mixture of several colors: we have no way of getting pure cyan, magenta and yellow paint.
So although in theory we can get a brilliant red from Magenta and Yellow, in practise this red will have some other color in it which will dull it, or desaturate it, or make it darker or paler. If we want a really vibrant red, we also need a red paint.
The same goes for blue and green.
So we need all six paints if we want to get the most saturated colors. In fact, high-end inkjet printers use at least these six color inks (and some of them add more inks) in order to produce the most saturated colors possible.
To get vibrant, saturated colors, we need Red, Green and Blue paint as well as Cyan, Magenta and Yellow paint.
This color wheel shows Yellow, Cyan and Magenta as the three primary colors. Red, Green and Blue are added because we can't get fully saturated reds, greens and blues from Cyan, Magenta and Yellow (at least not in traditional painting).
Red and Cyan, Green and Magenta, and Blue and Yellow are shown opposite each other because they are 'opposing' colors: if you add these opposing colors to each other in equal proportions the result will be black or gray (assuming that the colors are pure colors). They are called 'opposing' colors because they cancel each other out. For example, Red paint absorbs Blue and Green light (Cyan) and Cyan paint absorbs Red light, so (at least in theory, with pure paints) all of the light gets absorbed by Red and Cyan paint mixed in equal proportions. For the same reason Green and Magenta will also give gray or black, as will Yellow and Blue.
Note: I've put 'correct' in quotes because we can't really represent color on a wheel. And of course, in the real world there is no pure color, so the color wheel should only be used as a rough guide. But having said that, it is a useful one.
As a general rule, two colors that are adjacent to each other will mix to give a third color (so for example mixing Red and Yellow will give Orange), whereas adding a color to one that is more or less opposite it will dull or desaturate that color (so, for example, adding a bit of Cyan to Red will result in a less saturated, duller, red.
This is a correct color wheel:
I imagine that you must be wondering why I am wasting time with all of this color mixing stuff when we can pick the exact colors that we want using a color swatch and/or a color picker! AND, why not just use Cyan, Magenta and Yellow, since we are painting digitally?!
1. The biggest reason, and this applies more to watercolors than to any other medium, is that the paint mixes with other paint on the paper; and we often put down several layers of paint, to get the beautiful subtle hues that are such a wonderful characteristic of watercolors.
In this image I've splashed down some Ultramarine Blue, Indian Yellow and Crimson Alizarin (in Photoshop naturally) and blended them a bit:
You can see that even though there isn't all that much blending, the paints have mixed and made other colors, greenish yellows, oranges and deep purple blues.
As we let the paints blend together more, this effect becomes exaggered, but there is also a bit of muddiness that is creeping in, as you can see in the image below. The reason for that is that the particular colors I have chosen will become muddy: for example, Indian Yellow and Ultramarine Blue will give a muddy green, at best, as they are nearly opposite each other on the color wheel.
Well, of course, if this is a sky we are painting we probably don't want our paints to produce a vibrant green and we may be quite happy to have a darker desaturated bit of sky to give the impression of cloud, so these colors may be quite a good choice for a sky. But the important thing is to understand why some paints will mix well to give a good vibrant mixture and others do not.
2. A second reason is that even if we do pick the colors from our color swatch (and that's an excellent thing to do) we still need intermediate colors, so we still need to mix the colors.
3. As for the color picker: well, it's just too easy to pick any and every color and we can end up with too many colors in our painting, and, even worse, colors that don't work well together. It's usually better to pick out our color scheme first by selecting a few colors and then mixing these together to give further colors. If we do that then we will more than likely get good color harmony and balance. So even though this is a more complicated way to go, it's usually also a better way to go.
4. Mixing everything from Cyan, Magenta and Yellow in Photoshop is pretty much equivalent to using the color picker: the potential for getting too many colors or colors that don't work well together is very high. So again, it's a technique that is usually best avoided.
I won't go into how to select the colors for your painting as that is a whole subject in itself and there are plenty of tutorials available online. But I will give you these few tips:
And so, to summarise:
Last but not least!
To mix paint successfully, you should pick a basic round brush like the Mask Brush Soft and make sure to set the brush mode to Multiply. The Multiply mode in Photoshop really means Add, so by selecting Multiply, when we paint we are adding the paints to each other.
It's important that the underlying layer should be pure white with the blend mode set to Normal, otherwise the color of the underlying layer will get mixed with the paint.
In this example I have a stroke of Cyan on the top line, at 100% opacity. The first blob of paint at the top right is with Magenta at 100%, so we get a pure blue. Going left I've progressively reduced the opacity of the Magenta. On the next line down I've added Cyan to Magenta this time, going from 100% at the left and progressively reducing the opacity of the Cyan towards the right. The leftmost blob is 100% Cyan and 100% Magenta, so again we get a pure blue.
In this example I've done exactly the same thing, but this time with Cerulean Blue and Cadmium Yellow Pale. You may note that Cerulean Blue is much more of a Cyan than a Blue, which is why we get a nice green when we mix it with a yellow.
This is a good technique: all you need to do is to have the principle color at 100% and add the second color at varying opacities. As you can see in the examples above, I've also smudged the paints a bit using the Smudge Delicate: that's an additional method you can use, but it isn't necessary.
In the example below I've painted a strip of Indian Yellow at the top and then added Alizarin Crimson to it, starting at 100% at the left and going down to 20% at the right. As you can see, this gives a nice range of reds and oranges.
I've then sampled these colors, going from 100% down to 20% from top to bottom, giving a good range of tones. Using this simple technique we can get a large range of colors and tones.
And, of course, we can let the paints mix on the paper if we wish instead of pre-mixing them on our palette.
Mixing paint in Photoshop:
For more practical examples of how to set up your palette and how to mix colors in Photoshop, have a look at my tutorials.
I hope this article will help you to understand color better!