Adobe Illustrator CS4

PDF (adobe.com)

Color

Adjusting colors

Shift an out-of-gamut color to a printable color
Shift a color to a web-safe color
Blend colors
Change a color to its inverse or complement
Change the tint of a color
Invert multiple colors
Adjust color balance of one or more colors
Change the color mode of a document
Display and output spot colors using Lab values
Convert colors to grayscale
Convert grayscale images to RGB or CMYK
Colorize grayscale or 1-bit images
Adjust the saturation of multiple colors
Mix overlapping colors

community help (adobe.com)