Looking for Big's killers
Dressing ridiculous
Blue-and-red
Like I don't see what the big deal is

from Eminem – Marshall Mathers Lyrics 1 on Rap Genius

Meaning

Crips wear blue and bloods wear red: wearing the wrong colors in the wrong areas is asking for trouble. Em’s unhinged enough that he dresses in a way that’s guaranteed to piss off any gang members who see him

Interestingly, 2Pac also claimed to be both a Blood as well as a Crip; Eminem, in wanting to piss off both Bloods and Crips, could be paying homage

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