Colour Wheel or perhaps a Colour Triangle?
We may be familiar with the use of a "Colour Wheel" to explain colour. But, how easy is it to follow? Do we really understand it? Or, does it simply serve to confuse us?
In my tutoring experience, I find the latter is invariably the case. But perhaps now, there is a solution.
Remembering there are only three primary colours, wouldn't it be easier to form them into a triangle as seen above. Here we see a Primary colour in each corner, Secondaries (any 2 of the Primary colours) making up the sides and finally the Tertiaries (all 3 Primary colours) found in the centre.
Here, lighter tonal values are achieved by adding white. (or addition of water in the case of watercolour painting)