Head First HTML with CSS

overview of web colors
How do Web colors work?
You’re starting to see that there are lots of places you can add color to your
pages: background colors, border colors, and soon, font colors as well. But,
how do colors on a computer actually work? Let’s take a look.
100% Red 100% Blue
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100% Green
60% Red 60% Blue
60% Green
Web colors are specified in terms of how
much red, green, and blue make up the
color. You specify the amount of each
color from 0 to 100% and then add them
all together to arrive at a final color. For
instance if you add 100% red, 100% green,
and 100% blue together, you get white.
Notice that on a computer screen, mixing
together colors results in a lighter color.
After all, this is light we’re mixing!
Here’s red, green and blue being
mixed together. If you look at the
center you’ll see how they all add up.
But, if you add, say, only 60% of each
component (red, green, and blue) then
what would you expect? Less white,
right? In other words, you get a gray
color, because we’re sending equal
amount of the three colors, but not as
much light to the screen.