The Hue color component is used in the HSV (Hue, Saturation, Value) color model, which is an intuitive color model most often used by artists.
Hue represents an angle in degrees around an imaginary color wheel, where the colors appear in a "rainbow" fashion: Red (0º), Yellow (60º), Green (120º), Cyan (180º), Blue (240º), Magenta (300º) and back to Red (360º).
Black, white, and gray lie at the center of the color wheel.