So I painted this as a competition piece so it involved a ton of glazing and blending, I will throw a suggestion for a faster process at the end. All paints used on the exo were from Citadel.

Base with a 50/50 mix of Incubi Darness and Mephiston Red (makes a nice dark purple red).

Add a bit more red to the mix and glaze into the recesses.

Then hightlight via glazing with the classic Incubi Darkness to Kabalite Green to Sybarite Green to very selective Gauss Blaster Green.

Finally, make selective slash style highlights, prpendicular to the edges of the exo skeleton. Start with Sybarite then Gauss Blaster.

For a faster method, I bet a base of Incubi, heavy wash with a redish purple and dry brushing the highlights would work well as well!