In the land of Diablo III, enemies come in a few different colors. Normal, weak mobs are white, then there are those of color: I've seen blue, purple, and yellow. What do the different colors mean? Are there other colors?
A Blue colored monster is a champion. They come in packs and are guaranteed an item drop. Unlike their Diablo 2 counterparts they have no variants (e.g. posessed, ghostly, etc). They may have special attributes (such as extra fast, extra strong, lightning enhanced).
A Gold colored monster is a unique. It is a random spawning, randomly named monster with special attributes, usually accompanied by minions who share its attributes.
A Purple colored monster is super unique or a boss. These monsters have preset names and spawn in predictable locations. They have preset attributes which may or may not be shown under their health bar. They can be fully scripted and have unique models as well. Their item drops are usually tied to whether or not you have defeated the monster in the past.
Monsters with a white name are you run-of-the-mill monsters, the ones that are easy to kill.
Monsters with a blue name are champions. They normally come in a group of 3 or 4 and are a little tougher than those white monsters.
Monsters with a yellow name are Unique monsters, that come with their own minions who are tougher than the normal brand of minion.