Thanks for answering my first question, stemardue. What I was trying to do was entering the value manually which, for some reason, doesn't work. Your shader works all right. (and dividing by 0 doesn't freeze my Poser5. Which version are you on ?) Now, for my second question, is there a way to extract the Hue Saturation Luminosity values from a given color ? I read all the site you pointed to above, but it seems math functions cannot give the answer I seek...