The normal gooch shading essentially interpolates from the warm to the cool colors based on the dot product of the model normal and the light vector (N.L). So I decided to see what the results would be if I interpolated from warm to black to cool based on N.L. I figured that adding another color band would provide a greater range for the lighting interactions. Here is a sample of the output:
I like the way that the lighting is interacting with the model - particularly if the model is in motion. I have tried several different color combinations but the red/green seems to have a nice look to it.
There are a suprising number of different combinations that can be put together to come up with different effects. Another one that I have been experimenting with is to use the sum of the warm and cool colors as the mid-band of the color spectrum. It has turned out some interesting results as well:
Which do you like better or think provides better contrast for spotting the details of the model?