CSS: RGB Color
Hexadecimal Syntax
The RGB color model uses 3 values, for {Red, Green, Blue}, each with a value range from 0 to 255, in 2 Hexadecimal digits.
p { background-color: #ffd700; }
background-color: gold;
background-color: #ffd700;
Three digits Syntax Shortcut
if there are only 3 digits, it means doubling each digit.
p { background-color: #fd0; } /* is equivalent to */ p { background-color: #ffdd00; }
background-color: #fd0;
background-color: #ffdd00;