Killer Instinct

Colors for each character unlock at Level 3, so go into Survival or any of the fight modes and win 2 or 3 matches, preferably doing some of the fight challenges associated with each character.

If you're going to vote negative at least explain why(seriously, it will be interesting considering the guide is spot on)

Glacius earns a new color after lvl 3. You'll get enough XP for this while passively playing 200 matches. Idling is good enough for this achievement, but you will earn it faster while going for 10 survival wins.