I battled Root Aphids years ago... These guys are fucking monsters. I tried a lot of stuff and never managed to get rid of them until I removed all of the soil (and roots) from my garden by taking a brand new clone of everything in my closet. I studied them a lot.
The different colors come from them eating different stuff, their bodies are actually clear. They can be green/red/black/yellow, doesn't matter. When the colony outgrows it's pot they will swarm; they develop wings and fly around looking for a new plant to feed off, and will look a lot like fungus gnats at that point aside from the remaining crawlers.
If I encountered them again I would try beneficial nematodes. I tried Nuke Em, Azamax, and even some more aggressive methods that I'm not proud of employing and nothing really seemed to knock them back. Act now while the infestation is nubile.
Anyone else have any good ideas?