My favorite color system: HSL(A)

Selecting a color requires you to choose a color model . I am fond of hsla which I find logic to use.

Hue

Colors are arranged in a circle of 360°.
[hue]°

Saturation

How full of color should your color be?
[saturation]%
Zero is gray and 100% is full color

Lightness

How bright should your color be?
[lightness]%
0% is black and 100% is white.

Alpha

How transparent do you want your color to be?
[alpha]
1 = no transparency, 0 = fully transparent.
1 = fully opaque, 0 = not opaque.

CSS example of use:

.darkest {
  background-color: hsla([hue], [saturation]%, [Math.round(Math.max(lightness*.5, 0))]%, [alpha]);
}
.darker {
  background-color: hsla([hue], [saturation]%, [Math.round(Math.max(lightness*.8, 0))]%, [alpha]);
}
.color {
  background-color: hsla([hue], [saturation]%, [lightness]%, [alpha]);
}
.lighter {
  background-color: hsla([hue], [saturation]%, [Math.round(Math.min(lightness*1.2, 100))]%, [alpha]);
}
.lightest {
  background-color: hsla([hue], [saturation]%, [Math.round(Math.min(lightness*1.5, 100))]%, [alpha]);
}
Created using Mavo