Getting HSL from RGB

A visualization of how the red, green, and blue components of colors interact to create the full hue wheel.

The three primary colors are centered at 120º intervals. Each spreads a full 60º to either side (thus covering 120º total, or one-third of the wheel). Beyond each 120º wedge, the primaries fade from full opacity to complete transparency over another 60º to either side. The blending that occurs where these primaries overlap results in the full spectrum of colors shown around the individual color rings. The spokes mark 60º intervals.