From Ohio History Central
Color wheel.jpg
A color wheel or color circle is an organization of color hues around a circle, showing relationships between colors considered to be primary colors, secondary colors, complementary colors, etc.

The hue seen when looking at the surface of a mineral in daylight. In many minerals, color will vary in specimens from different localities, usually resulting from chemical impurities. When looking at color, the observer always should examine an unweathered surface.