Color 
color: value;

To add color.

Colors CSS
rgb() 
color: rgb(0, 0, 255);
color: rgb(0%, 0%, 100%);
color: rgb(0, 0, 255 / 0.5)
color: rgba(0, 0, 255, 0.5)

Select colors using red, green, and blue light mixtures. Alpha is opacity. Written in different ways.

Colors CSS
opacity 
opacity: 0.5;

Set the opacity of an element

Colors CSS
Color Names 
color: red, blue, yellow;

Use color keyword names to bring colors.

Colors CSS
hsl() 
color: hsl(360 50% 50%);
color: hsl(240deg 30% 60% / .7);
color: hsl(240 50% 50% / 25%);
color: hsla(240 50% 50% 0.5);

Select color using it's hue, lightness, and saturation. Alpha is optional transparency.

Colors CSS
Hex Colors 
#RGB        // The three-value syntax
#RGBA       // The four-value syntax
#RRGGBB     // The six-value syntax
#RRGGBBAA   // The eight-value syntax

Select colors using hex codes.

Colors CSS
Color Keywords 
color: transparent;
color: currentcolor;
color: inherit;

transparent - have no color, transparent
currentcolor - current color being used in element
inherit - to inherit the color from the parent element

Colors CSS