Actually, i think it tiers based on your stats. I've had mobs that were red and yellow when i was rank1/level1 that show up as yellow green and blue when i was r1/lvl12 on a different class.
I could be wrong though.
Try it with a class you do not have leveled and you'll see what i meant.
Con shows green as level 9 Thaum. Switch to Level 1 Conjurer and it's now red. Same stats, just changed the weapon in main hand to a non leveled class. Same stats all together.
Edited for pelling.... should post slowly Edited, Oct 1st 2010 5:06pm by Vladislaus