Color-coded NPCs

Video game concept

NPCs are color coded for how tough they are or otherwise identify their nature, such as element.

Shaiya (Windows)
WIN 2005-10-21
Alien Shooter: Vengeance (Windows)
WIN 2007-02-05
Völgarr the Viking (Windows)
WIN 2013-09
Lord of the Rings Online (Windows)
WIN 2007-04-24
Recettear (Windows)
WIN 2007
Halfway (Windows)
WIN 2014-07-22
Alien Shooter - Revisited (Windows)
WIN 2009-04-15
DmC Devil May Cry (Windows)
WIN 2013-01-25
DmC Devil May Cry (PlayStation 3)
PS3 2013-01-15
Ghostbusters: Sanctum of Slime (Windows)
WIN 2011-03-23
Neuro Hunter (Windows)
WIN 2005-09
Dead Space 3 (Windows)
WIN 2013-02-05

The first video game about Color-coded NPCs was released on June 28, 1991.

Sigma Team, Eidos Interactive and QCF Design has published most of these games

This is common in MMOs but usually limited to the ever present name tags that float above every critter you encounter.

Older games with miniscule graphics (in terms of used pixels) often resorted to palette switches for sprites, which usually matched how much tougher the individual variant was. However, this does NOT require palette swapping to be involved. The colored enemies can be wholly unique, they just have distinct coloring to show other traits.