Hey, Humey. I'm glad you liked my Sons of Medusa. Here's my entry for your Deathwatch force
I used Reaper Master Series paints:
Green: jungle green for the base, midnight blue for the shadows, and jungle moss and a light grey for the highlights
White: I painted this with bone - bone shadow, aged bone, and polished bone
Black: black (of course!), midnight blue, and a medium grey
For
GW conversions... my best guess is
Green: Base - Incubi Darkness, highlights - Warboss Green or Kabalite Green then a touch of Slaanesh Grey, shadows - Darkenhof Nightshade
White: whatever you use for bone, screaming skull and shadows/highlights of your choice
(or you can go emerald green and bright white for a more traditional Sons of Medusa marine)
The Sons of Medusa like their devastator squads, so anyone carrying a heavy weapon of some sort would be a good candidate. They also strive to get rid of any weakness, so robotic arms, legs, eyes, etc are very common. Oh, and instead of 10 companies, the Sons of Medusa are organized into 3 war clans (so if you add any numbers to him make it 1, 2, or 3).