Look at the NSColor Class Reference "Changing the Color" section. There are several methods to make a new color form existing one:
– blendedColorWithFraction:ofColor:
– colorWithAlphaComponent:
– highlightWithLevel:
– shadowWithLevel:
Also you can create a new color with RGB components calculated from your existing color (or HSB components) with
+ colorWithCalibratedHue:saturation:brightness:alpha:
+ colorWithCalibratedRed:green:blue:alpha: