Crib Sheet

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Mixing Colours

When we talk about mixing colour, we generally mean mixing pigment. This is called subtractive mixing, and it's what this cribsheet is about. Mixing light - additive mixing - will be dealt with in our cribsheet on light.

When white light hits a coloured surface, most of it is absorbed; but some of it is reflected - and that's the part we can see. Thus, a green object reflects green light but absorbs all the other wavelengths.

When we mix pigments, more light is absorbed. If you could mix paint perfectly, it would be black - all the light would be absorbed. This is why mixing pigment is called subtractive mixing.

There are some colours of pigment you can make by mixing other colours, and some you can't. Those you can't make are red, blue and yellow. They are called primary colours. The colours you get when you mix any two of them are called secondary colours. Here's what you get:

Red and Yellow = Orange

Yellow and Blue = Green

Blue and Red = Purple (or sometimes brown, depending on the primary shades you use)

Obviously, the exact shade you get depends on the colours you start with, and the proportions you mix them in. It is possible to make a colour wheel, in which the colours are graduated into each other.
This works best if you have a true primary red, blue and yellow to work with - ask for advice in an art shop, if you aren't certain what to use.

Start by cutting out a circle of card. Divide it into three with pencil lines. Paint over each line with a strip of red, blue, or yellow. Now, starting with the red, carefully blend in a little yellow. Paint in a stripe of that colour. Then mix more and more yellow with the red, painting a stripe of each colour on your wheel, until you get a pure yellow. Now start mixing in blue - again, paint stripes of the colours you make, until you arrive at pure blue. Then work from blue to red.

If you look at your colour wheel, you'll see that the contrast between colours directly opposite each other is particularly strong. These are called complementary colours - thus, red is complementary to green, and so on.

There is one other property of colour you can explore, and that is saturation. This means how much white the colour is mixed with. You can explore this by making a colour bar that graduates from any strong colour (not necessarily a primary colour) to white, and back again.

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