Guild Wars 2

I was thinking, how fitting it would be if my Sylvarri guardian emitted green effects instead of blue. Someones preference might be red, orange, or something else. Purely cosmetic, but i think it would add more variety and give new character ideas (in a pure RP sense)

The devs have done a good job tying specific colors to specific professions. This helps other players read the game. In PvP and WvW it would make things more difficult for your opponents (unfairly so, probably) and in PvE it makes things difficult for your allies.

This has been discussed before and the Devs said no for pretty much all the reasons stated above.