So one of the colours has to be green (skin) and the bases could be green.
I noticed on Sunday most of the Orks were undercoated black (and the Gretchin white).
I'm not sure what colours the clans are now, but when i did my Epic40K orks:
Deathskulls - blue (scavengers)
Goffs - black (hard as nails)
Evil Sunz- red (speed freaks)
Bad moonz- yellow ( rich Orks...loads of HW )
Snakebites- brown + grey (old school types)
blood axes- human camouflage patterns (mercs)
So the hardest ones to do would be the Blood Axes...but they are not real Orks anyway (according to the old fluff)
So a unit of Goffs would be the easiest.
Set them up and do a production line run of one colour, start with green and do all the bases to get the paint consistancy right. Then do all the arms and faces. Easier said than done i know. Dont bother with eyes or teeth or details of any kind.
Then do the guns in a contrasting colour , maybe red or yellow.
Finally , as you were going so fast they are all a bit messy ...so go round the colours you have done with some black.
And tidy them up.
i reckon you could have a unit done by the end of the week without really killing yourself.
Added (14-Dec-2009, 10:57 Am)
I'm a cheat! I recommend the dipping method
You still need to paint them first in at least block colours before you dip them ,Big G