You're an ace! thanks.
i had started hacking at your color-by-Z yesterday, learning ruby as i go, and managed to make color by steps, meaning it will ask you how many maximum colors you want and color the slopes accordingly. i couldn't figure out how to get the angle of the normal though until you posted this today. i had been using the z of the vector instead of its angle, so the results were off.
anyway, i finally merged both your plugins into the attached aa_color_by_slope.rb. i hope you don't mind, it's yours of course.
i made it ask for the start and end colors and the number of segments (max colors), which i limited to dividents of 90 to reduce hassle. i still don't understand why i can't get the 1st color the same in all variations on the numbers (for example if you go with green to red, and do tests for 2, 3, 9 segments, you will see that sometimes the starting green changes, although it shouldnt)
finally, thanks again for this Chris, and TIG: your ideas rock! (no pun intended, but i'm using this precisely to figure out buildable areas on a rocky site )
-aa
EDIT: file removed, please see top post for download link