W3cubDocs

<hex-color>

The <hex-color> CSS data type is a notation for describing the hexadecimal color syntax of an sRGB color using its primary color components (red, green, blue) written as hexadecimal numbers, as well as its transparency. It can be used everywhere a <color> type is allowed.

A <hex-color> value can be used everywhere where a <color> can be used.

Syntax

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

Value

R or RR: The red component of the color, as a case-insensitive hexadecimal number between 0 and ff (255)). If there is only one number, it is duplicated: 1 means 11.
G or GG: The green component of the color, as a case-insensitive hexadecimal number between 0 and ff (255)). If there is only one number, it is duplicated: c means cc.
B or BB: The blue component of the color, as a case-insensitive hexadecimal number between 0 and ff (255)). If there is only one number, it is duplicated: 9 means 99.
A or AA Optional: The alpha component of the color, indicating its transparency, as a case-insensitive hexadecimal number between 0 and ff (255)). If there is only one number, it is duplicated: e means ee. 0 represents a fully transparent color, and ff a fully opaque one.

Note: The syntax is case-insensitive #00ff00 is the same as #00FF00.

Examples

<p>Hexadecimal syntax for a fully opaque hot pink</p>

<span>
  #f09
  <div class="c1"></div>
</span>
<span>
  #F09
  <div class="c2"></div>
</span>
<span>
  #ff0099
  <div class="c3"></div>
</span>
<span>
  #FF0099
  <div class="c4"></div>
</span>

div {
  width: 40px;
  height: 40px;
}
.c1 {
  background: #f09;
}
.c2 {
  background: #f09;
}
.c3 {
  background: #ff0099;
}
.c4 {
  background: #ff0099;
}

Specifications

Specification
CSS Color Module Level 4 # hex-notation

Browser compatibility