How often do gangs use clothing to identify themselves?

I'm doing a debate on uniforms in schools. I'm the affirmative side (meaning that my team wants uniforms in schools), and one of our points is that by wearing uniforms, kids can't wear certain colors of types of clothing as a way to identify themselves as gang members. I was wondering if anyone knows of any studies done, that show how often gangs use clothing as a way to identify themselves.