Not a racist term, but a product of drinking booze THEN puffing the cheeba.
It's name is based sround the fact that you:
a) go white
b) see nothign but stars (white or green ones) and promptly spazz out on the floor, sometimes accompanied by vomiting and the farts.
"Chrissy just took a huge bong hit and threw a whitey,... think he's in the toilet driving the porcelain bus."