Just a note: The colors he sees are the "real" colors associated with each form of magic... not he color that has been attached to it because it sounds nicer.
"White" mages are the only ones who can cast the spell that would allow them to see magic in this way, so they were the ones who got to set what color is what. They thought "purple" magic sounded funky, so they re-labeled it black. Also, who would want to call their own color yellow?
I will note that my "extras" section on magic does not mention this... The "author" was a white mage who thought it was a fun joke to keep people in the dark... The borders around the relevant gems show the true colors however.
A summary, a long with a couple examples of each:
Black is really Purple, and is force magic. (Magnetism/Gravity)
Red is energy magic. (Fire/Charge)
Blue is current magic. (Momentum/Weather)
Grey is mind magic. (Illusions/Memories)
Green is body magic. (Nature/Healing)
White is spirit magic. (Dispel/Spirit)
I N F O R M A T I O N
On hiatus. Updating sporadically while the next arc is worked on.