The colors of magic do seem meaningful, but we’ve seen Rumple use almost every color of magic there is. (Usually purple, but also red, blue (healing particularly), and black that I can remember off the top of my head.) Cora and Regina mainly use purple, and Zelena and Pan mainly use green, but I don’t think that their magics are limited to those colors either.
Sometimes the colors the people use are more keeping with traditional images of them, though.
Cora uses red as well–but she’s the Queen of Hearts and wore a TON of red once she took over WL. It’s her power color.
Zelena and Pan both use green but I wouldn’t have expected them to use anything else because both are associated with green (Pan wears green, the WWW is green…)
With Emma, I honestly expected her magic to always be white/rainbow because she’s TL incarnate so the color magic in 222 confuses me.