I didnt use any light filling (except for the for the default sun).
Your desaturated picture looks good.
I will build a colour-gradient with 6 colours, somewhat simplified.
I love the node network
I have 2 problems with using the colour mixer in my gradient network:
1. mix is linear in luminosity. E.G. A mix of pure red and pure red with a control of 0.5 gives a color of 128,128,0 (luminousity=64)
pure red and green has a luminousity of 128, so i would expect the luminousity of the mix to be pure yellow instead of unsatureded yellow.
2. The mixer clamps the controller to 0 for negative values, but does clamps the controller to 1 for values > 1