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.
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Keeper of Belle's Gold magic, sand dollar, cloaks, purple FTL outfit, spell scroll, library key, copy of Romeo and Juliet, and cry-muffling pillow, Rumple's doll, overcoat, and strength, and The Timeline. My spreadsheet: https://drive.google.com/file/d/0B6r8CySCCWd9R0RUNm4xR3RhMEU/view?usp=sharing