Red yellow and blue, the 3 primaries from which other colours can be derived. So seemingly simple.
But WHICH red, yellow and blue? And why do the primaries not always make clean colour? You may have found that mixing one type of blue with another type of red does not make a vibrant purple but a dull one. Or you may have tried making a fresh bright green that turns out olive. This is because one or both of the colours you have chosen contains a bit of the other colour's complement which will dull a colour. Let’s use red and blue as our example. Mixing cad red light with ultramarine blue will not make an intense purple, it will make a very dull greyed purple.
So why does this happen? It’s red and blue after all. Cad red light has a yellow/orange bias, when mixed with ultramarine blue (orange being the complement of blue, and yellow and blue making green) it will not make a real purple but instead a dull greyish purple. On the other hand a quinacridone rose which has no yellow bias makes a great purple when mixed with ultramarine blue which is a blue containing no green, in fact it has a red bias. Quinacridone rose is closer to blue on the colour wheel than is cad red light.
Lesson: choose colours closer in proximity on the colour wheel for fresher more pure colour.
But there are no absolutes and occasionally you will find that this rule does not apply.
Lesson: choose colours closer in proximity on the colour wheel for fresher more pure colour. But there are no absolutes and occasionally you will find that this rule does not apply.