Vincent Van Gogh understood color so well that he made paintings that dissected the essence of our color perception. He was hanging with Seurat and Toulouse-Lau

Vincent Van Gogh understood color so well that he made paintings that dissected the essence of our color perception. He was hanging with Seurat and Toulouse-Lautrec and Gaugin. He wrote thousands of letters, mostly about his paintings and the usage of color, and his painter friends wrote him back. Quick excerpt of a letter to Theo: "I still often run up against a blank wall when undertaking something, but all the same, the colours follow one another as if of their own accord, and taking a colour as the starting-point I see clearly in my mind’s eye what derives from it, and how one can get life into it. Jules Dupré is like Delacroix in landscape, for what enormous diversity of mood he expressed in symphonies of colour. Now a seascape, with the most delicate blue-greens and broken blue, and all sorts of pearly tones. Then an autumn landscape with foliage from deep wine red to vivid green, from bright orange to dark havana, with yet more colours in the sky in greys, lilacs, blue, white, forming another contrast to the yellow leaves. Then again a sunset in black, in violet, in fiery red. Then again more capricious, like the corner of a garden by him that I saw and have never forgotten; black in the shadow, white in the sun, bright green, a fiery red, and then again a dark blue, a bituminous greenish brown and a light brownish yellow. Truly colours that can have quite a lot to say to one another." Here's the most important part of that letter: "Still, it doesn’t satisfy me. To my mind there’s far more behind not doing it in the local colour. True painters are the ones who don’t do it in the local colour — that was what Blanc and Delacroix discussed once." At the time the impressionists were discovering that our color sense is counter-intuitive. They were developing methods of painting a color by using contrasts near a gray to imply the inverse color, etc. That's what he means by not "[doing] it in the local color." You put red by gray and the gray looks green by contrast. To look at those paintings and say "I guess he painted this way because he couldn't see the color right" is incredibly ignorant. His choices were deliberate and he documented them in excruciating detail.