If you’re one of the few crazies like me who prefer doing web development using command-line tools, you might appreciate this simple command-line calculator which can operate on RGB colors. It supports the 4 basic arithmetic operations and grouping using parens. Examples:
C:> colorcalc FFFFFF / 2
You can use scalar values, as well.
C:> colorcalc 808080
Since 0 is #000000 and 1 is #FFFFFF, 0.5 is between #7F7F7F and #808080.
C:> colorcalc 808080 * 808080
Vector-ish multiplication – approximative equivalent of 0.5 * 0.5.
C:> colorcalc 1-FFCC00
Get the negative of a color.
C:> colorcalc (FFCC00 + CCDDFF) / 2
Calculate the mean value of two colors.