I have noticed that the treasure goblins have different colors. Some are red, blue, yellow, black and so on. Do the colors mean anything? Does it mean they have different loot? Sometimes treasure goblins tend to drop gems, other times books/pages. Can this have anything to do with the color of the goblin? Are they harder to beat or what does it mean?
Check out this post on Treasure Creatures.
Of note is the following graph that shows some interesting trends for the different goblin types.
It looks like the loot distribution depends on the name, not the color. Take this data with a grain of salt though, the sample size was fairly low.
There is a rumor that it correlates to what kind of loot they will drop:
- Blue = magic item(s)
- Yellow = rare item(s)
- Green = set item(s)
- Gold = Legendary item(s)
This is a very tempting thought, but it has been tested to be untrue. Here is a thread where some of the testing is done, that disproves blue = magic only, gold = rare, etc.
I cannot find any other information on how their colors or names are chosen, but here is some more information on how they work in general: How do the Treasure Goblins work?
The only thing that can be safely stated for now is that the color doesn't seem to have an effect on the health of the goblin (you can turn on monster health to see how much HP they have). All the various colored goblins I've ran into in one area (A3 inferno) had roughly the same health (800k).
There are a lot of speculation but not enough data to say for sure whether or not the color of the goblin will give you a greater chance to drop a particular quality of loot (rare, legendary, magical, etc).