Hello fellow earthlings. A quesion about RGB color and its usefulness in a simple tiny php code:

Imagine I have variable $colorA containning a valid six char color. say B1B100, a greenish natural color. Now If I would like to make a new color from that, which is, say, ten steps lighter thatn that original color, roughly.

$colorA = B1B100 // original color
php code with little color engine lightening stuff up goes here
$colorB = ?????? // original color lightened up

Is there a php ready function that KNOWS rgb colors something like

php function RGB ( input color, what to do, output color) Where what to do could be +/- 255 values of brightness etc etc.

Is something like this already possible or am I day dreaming?

rgb($colorA, +10, $colorB)

If this does not exist, what would be the shortest code for doing this? Link suffices. Suggestions and ideas are answers to me. Thanks.