The Color Wheel
There are also definitions (or categories) of colors based on the color wheel. We begin with a 3-part color wheel.
In traditional color theory (used in paint and pigments), primary colors are the 3 pigment colors that cannot be mixed or formed by any combination of other colors. All other colors are derived from these 3 hues.
These are the colors formed by mixing the primary colors.
Tertiary Colors: Yellow-orange, red-orange, red-purple, blue-purple, blue-green & yellow-green
These are the colors formed by mixing a primary and a secondary color. That's why the hue is a two word name, such as blue-green, red-violet, and yellow-orange.