Color structure valuation is taught through the color wheel
The primary colors, yellow, red, blue, and secondary colors, orange, green, violet, are invariably included in such a chart. But it usually also includes expanded mixtures of at least twelve hues. From this simple chart of a color wheel, multiple variations of color hues can be developed, which may or may not suggest to each other under certain circumstances. The judgement of the eye is usually checked on by the hand by actual touching. Is it really smooth, or does it just look that way? Is that an indentation or a raised mark? No wonder there are so many "DO NOT TOUCH!" signs.

