She from Grape Street, she know how to work the mag
And only buy white tees, tell 'em to keep the purple tags

from Game (Ft. Nate Dogg) – Where I'm from Lyrics on Rap Genius

His girl comes from Grape Street, an infamous set of the Crips located in the Watts district, California. They wear purple rather than the traditional Crip blue. So there is the reference to the purple tag.
Mag is an abbreviation for Magnum (the handgun)

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