convert Scalar values to that smooth red blue green scale that 3d plotters use

I want to plot a 3d graph. but I want to scale the colors according to that real smooth transition from red to orange to yellow (a rainbow type tranisition) … you get the point.

What is the rgb format of such a transition so that I can convert some scalar value to color values …

[This message has been edited by delic (edited 10-24-2002).]