I paint a lot of minis, and most of them are troopers for one game or another. That's not really surprising, because in most games you'll have a few characters and a lot of grunts.
For different factions and different games, the fluff changes as to just how unified a force should look. Everything from Warhammer 40,000's codex chapters with their matching color coded shoulder pads and helmets, to Malifaux's loose affiliations of mercenaries and scum. Sometimes you paint all of the troopers the same, and other times you pick colors or styles that tie the troopers together.
My wife and I decided that for our Super Dungeon Explore set, we weren't going to tie the minis together in usual ways. Rather, the minis were going to tie together stylistically: each and every Kobold will be a different color, but they will all be painted using black lining and color book-ending.
That reminds me that I'll need to do a write up on the bookending with a little show and tell. It is a technique that I learned that helps make minis look brighter. Here are the first three finished Kobolds. If you know just how bottomless the pile of Super Dungeon minions is, you'll know there's more on the way.