Here's the shader. The numerical and color values don't matter much - it depends on your map and what colors you want.

The map I had was green. Using HSV I shifted it to blue and magenta.

You run your variations into a ColorRamp, which is driven by Edge_Blend. The Edge_Blend changes value based on viewing angle.

Specular also changes value based on viewing angle and light source angle. I did one branch with Diffuse and one branch with Specular. Mix and match to whatever goal you want.

There is no math here - you see what you're going to get in real time.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)