You do see some of what Americans would classify as gang graffiti in China but this traditional kind is not done at night with spray paint and gang colors, it is done during the day with water, brush and suit and tie.
I found a web site that referred to graffiti in China and also had a lot of good links if you are interested in this type of art.
http://microscopiq.com/2006/12/chinese-graffiti-stories/
