Sorta simple scheme for Bad Moon Ork Boys, for this tutorial I will use a mixture of traditional and "contrast" paint

1. Undercoat the model in a light undercoat such as Corax White Wraithbone or Grey Seer
2. Paint the teeth and any rags on the ork boy with Skeleton Horde
3. Cover the exposed skin in either Ork Flesh or Waaagh! Flesh , wait for it to dry then clean up any parts that shouldn't have been painted green with whatever undercoat you used.
4. If you're using a white undercoat I strongly recommend cleaning your brush under a tap instead of in your water cup so that you don't contaminate your white colour with your green.
5. Decide what part of the clothing should be yellow and paint it. I personally recommend using Averland Sunset for this but f you war a less warm colour you could use Yriel Yellow , just keep in mind that it's a layer paint and you might need more layers of paint to get a good coverage
6. Paint the clothing you didn't chose do be yellow black, I use Abaddon Black for this but Corvus Black would probably also work
7. Paint the metal parts using Leadbelcher and Retributor Armour
8. Shade the miniature with Nuln Oil for the silver, ork skin and black parts, Reikland Fleshshade for the gold parts and Casandora Yellow for the yellow parts
9. Optional: If you're feeling extra fancy highlight all the Skeleton Horde parts with a white layer paint such as White Scar
10. Highlight the Yellow with Yriel Yellow unless you used it for the base coat in which case highlight it with Flash Gitz Yellow instead
11. Highlight gold parts with with Auric Armour Gold and the silver parts wth Runefang Steel
12. Highlight the ork skin with Warboss Green