In a letter to his brother Theo in 1882, Van Gogh wrote: "There are but three fundamental colours – red, yellow, and blue; 'composites' are orange, green, and purple. By adding black and some white one gets the endless varieties of greys – red grey, yellow-grey, blue-grey, green-grey,orange-grey, violet-grey. It is impossible to say, for instance, how many green-greys there are; there is an endless variety. But the whole chemistry of colours is not more complicated than those few simple rules. And having a clear notion of this is worth more than 70 different colours of paint — because with those three principal colours and black and white, one can make more than 70 tones and varieties. The colourist is the person who knows at once how to analyze a colour, when it sees it in nature, and can say, for instance: that green-grey is yellow with black and blue, etc. In other words, someone who knows how to find the grays of nature on their palette". Keep reading this article.