RGBColor makes colors from red, green and blue color component values. The component values range from 0 (none) to 1 (full). This gives red, because only the red component is nonzero:

When all of the components are 0, you get black:

When all of the components are 1, you get white:

Mix different amounts of red, green and blue to get different colors:

There are “color spaces” other than RGBColor that specify colors in different ways.

Hue makes colors from a hue value (the color), a saturation value (how intense the color is) and a brightness value (how dark or light the color is).

Here is red in the Hue color space (also called “HSB”):

Use a smaller saturation value to get pink:

Use colors to style text or color graphical elements. This makes red text:

This makes a blue disk: