Not by the colour of their skin; there is only one nation that makes me racist: Americans. So, I label people by:
a) their look (it's not about being poor) - if they look like an emo, techno-lover, rap-lover or a plastic girl, I automatically think: idiot.
b) music they listen to
c) their political views
d) religion - well, I discriminate everyone who talks about religion or wants to convert me.
e) in case of the USA, country they come from.
f) their age - because many kids and junior high school kids are just idiots without brains.