Well, here is a red ork i painted quite a while ago
Not the best paint job, but it gives the gernal idea!
Best way to paint red skin is start off with Gore red base, then give it an asyluum blue wash (spelling?), then blood red highlight (remember to avoid all crevices) Fourthly, add an highlight of blazing orange, and you should be good!
If you want to tone it done, wash with badab black wash after the orange is done.