You can tint Hawk Turquoise with Rotting Flesh or Space Wolves Grey. Both provides nice cool highlights, with Rotting Flesh erring towards green and Space Wolves Grey towards blue.
Highlighted with Rotting Flesh:
Highlighted with Space Wolves Grey (and Skull White for the final highlights):
You can shade it by adding Regal Blue (for a blue), Orkhide Shade (for a green) or Warlock Purple (for a muted, neutral effect – as seen on Alpharius).
Warlock purple makes a nice complement, too.