So for the color:
I mainly use 3 different mark of paint and water
No add
I use P3, master series paints from reaper, and Games of course

The blue chitin receive a base of a mix from cygnar blue (ultramarine blue )+ chaos black + frostbite (space wolf grey) + aqua surf (ice blue)
The shades had been done with the base + more black in it
To blend the base and the shade I use intermediate tone done with base + amethyst purple (MSP master series paint )
The first highlight contain the base + frostbite and final highlight with only frostbite very diluted ( 1 paint 10 water)

Now the pallid skin:
Base done with menoth white base (P3) + codex grey
First shade done with base + night shade purple (MSP)
Second shade done with base + black
First highlight done with base + frostbite
Second highlight done with menoth white highlight (the same as before 1 paint and 10 waters)
Then I apply everywhere very thin glazes of different color to re hot the pallid tones, I’ve put some clear purple, bright blue, and yellow glazes
Unfortunately they didn’t appear on the photo and that why it looks flat (I know I’m never happy ^^ )