Here's how I paint my zombies.
Stages:
1. Undercoat white.
2. The skin! I can't really remember exactly how I did it but that doesn't matter as there's supposed to be variety! For a greenish skin use Rotting Flesh as a basecoat on all the skin areas. For a more pinkish skin use Pallid Flesh.
3. Highlight the skin by mixing a little Bronzed Flesh in with whichever 'dead' colour you used, and drybrush it over the raised areas.
4. Paint the clothes. I used Scab Red and Chaos Black, alternating between trousers and torso i.e paint one zombie's trousers red, then another's shirt red, then paint the first shirt black and the second's trouseres black. I haven't highlighted yet, and I don't know if I will, but if I decide to I'll ad it when it's done.
5. Paint the weapons boltgun metal.
6. Cover any leather or wooden areas, and the shoes, with Vermin, Bestial or Scorched Brown. I varied between each zombie.
7. Paint the hair whatever colour you like. Use a few different colours throughout the regiment.
8. Paint the bone areas in the same as for skeletons.
9. Paint any guts by mixing red and blue to get a purplish colour, and highlight up from there by adding more red.
10. At this point I will add some blood. I haven't got there yet but when I work out a way of doing it I'll tell you. This part is optional anyway, as some people like their zombies 'clean'.
11. Sit back and admire. As long as it worked that is.

A couple of almost finished zombies, one with pink skin, one with green. I still have to tidy them up and do the bones, blood, and face detail.