First of all, no color from the original spectrum has any higher claim to be a primary color than any other. Each hue occupies an equally legitimate place on the outer rim of the hue circle and can claim full status as a primary color. Nor are any particular hues by their nature secondary colors. Green is not a composite color any more than blue is. You could set up a palette with high-chroma orange, violet, and green as primaries and paint a satisfactory image from them. It’s a good painting exercise to do so, and it can result in a perfectly acceptable painting.*
Secondly, it turns out that the traditional YRB wheel is out of proportion, like a clock face with some of the numbers bunched up in one corner (see center of wheel). It expands the yellow-orange-red section of the spectrum too much, so that red is at 4 o’clock instead of 2, and blue is at 8 o’clock instead of 6. This uneven distribution came about partly because our eyes are more sensitive to small differences among the yellow, orange, and red hues, and partly because pigments are more numerous for warm colors, compared to cool ones. The precious pigments Vermilion and Ultramarine became our mental image for red and blue. There have always been many available pigments for the oranges and reds, but few for the violets and greens.
So, are primaries all relative? Can we set up the color circle in a different way? The answer is an emphatic yes. Tomorrow we’ll look at the Munsell system, which has served as the color map for many great realist painters.
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*In the case of mixing colors from OVG secondaries, you’ll have a hard time mixing a pure yellow, because yellow is a special case: it’s purest form is much lighter than the pure form of other colors, so it isn’t easy to mix yellow as a secondary in pigments. But the OVG colors have been used as primaries for the autochrome photo process.
Reviewing the posts in this series:
Part 1: Wrapping the Spectrum
Part 2: Primaries and Secondaries
Part 3: Complements, Afterimages, and Chroma
Part 4: Problems with the Traditional Wheel
Part 5: The Munsell System
Part 6: Cyan, Magenta, and Yellow
Part 7: The Yurmby Wheel
