HTML and CSS Reference
Figure 6-23. In an additive color model, the primary colors add to the lightness of each other.
Within CSS, color is commonly defined using hexadecimal notation . This notation
breaks the red, green, and blue components of a color into two-digit numbers that togeth-
er result in a six-digit number preceded by a hash sign, in the form #RRGGBB . Called a
hex triplet , each digit pair has the hexadecimal numerical range of 00-FF. For example,
#ff00ff represents full-intensity red and full-intensity blue, without any green. Com-
bined, they produce magenta. If you are unclear of how this sequence of numbers and
letters becomes a color, be sure to read the "How web color values are calculated" side-
bar for more information.
HOW WEB COLOR VALUES ARE CALCULATED
All the colors you see displayed on your screen are composed of the three primary
colors red, green, and blue. As shown in Figure 6-23 , it is an additive color model,