Here's a mini that I painted recently for my own Space Hulk set. For the colors, I went with a dark magenta rather than the cadmium red that I normally associate with the Blood Angels. I mostly did this to have a big change from the Space Hulk sets that I've painted for commission.
After painting that up, I realized that in order to really bring forward his composition, the other colors needed to be rather light.
The jewels especially worked well to this end. Most of the time, when I paint jewel effects, I use pure black as the darkest shade. This time, I decided to use a bright base color as the darkest shade, overall giving the jewels a much brighter look.
I really feel that this helped all of the many details on this mini to pop.