Introduction

CSS3 brings with it support for some new ways of describing colors on the page.

Before CSS3, colors are declared using hexadecimal format (#FFF, or #FFFFFF for white) or rgb() notation, providing either integers (0–255) or percentages or using named colors.

example
hexadecimal - #FFFFFF
rgb - rgb(255,255,255) or rgb(100%,100%,100%)
named colors - purple, lime, aqua, red

CSS3 also provides us with a number of other options: HSL, HSLA, and RGBA. The most notable change with these new color types is the ability to declare semitransparent colors.
Related Tutorial
2. RGBA
3. HSL
4. HSLA