As far as I know, the meaning behind the colored smoke has never been explained. Each magic user seems to have their own personal color that tinges the magic they do, but if there is any deeper meaning to those colors it has not been specifically addressed.
It has been addressed that the colors are intentionally distinct. Regina recognizes the "green smoke" as being a signature of the Wicked Witch from Oz.
The colors do seem to be chosen intentionally to represent the person that uses them. Zelena's entire motivation now is jealousy (of Regina) so green fits her well, and Rumple is a very angry person, so he gets red. But I don't think it's as simple as the user's emotions choosing their color: remember that Zelena's magic was always green, long before her jealousy emerged and caused her skin to change. And Regina's purple smoke is the color of royalty, fitting her status as Evil Queen, but doesn't really match any of the emotions she tends to exhibit.