Simply replace suit1blue.txd with suit1blue.txd in IMGtool. Then go in Didier Sachs in Downtown, Los Santos and buy a blue suit, along with black shoes. Go the Victim next to it afterwards and buy black pantsand if you want a gold watch.
Congratulations, you're now dressed as a Nigrabut you aren't one yet. Go to Reece's Hair Facial Studio (the one you went to in the beginning of the game). Get any kind of afro cut you want (nothing, beard, or 'stache). Now you are ready to reak havoc and lulz.
http://www.encyclopediadramatica.com/images/f/fc/Poolsclosed.jpg
There is a bonus haircut which is the same one that Samuel L. Jackson has in Pulp Fiction. Replace afrogoatee.txd with afrogoatee.txd, and it will replace the afro with a goatee just in case you couldn't figure that out.