scarab/raven PAINT question?

Maybe try a layer of transparent blue over the black? It might catch blue in certain light. However, you'll want to test that out first since I can't guarantee it'll work (if the blue is too thick, maybe a wash of transparent blue would work). If you have an airbrush, maybe airbrush dark blue streaks. It'll be more apparent but airbrushing blends into the next color well and might be the best option overall. Adding a little bit of blue to the black before painting won't hurt the cause, either. Drybrushing very lightly with a very dark blue might also help.

I;m not certain any of these will work, but I have the same issue coming up with my next figure where I'll have to do neon green on black and I have to figure out how to make it look naturally flowing rather than artificial lines and I'm going to try these steps myself (maybe not the mixing into black paint, but with a dark color like sapphire it'd likely work better).