<3 Revolution Cafe. Last time I tried to go to one of these, I didn't know who anyone was and if they were for the meetup. I know it's corny, but should there be a designated meeting color? Orange?
Next time, just walk up to people and introduce yourself. Why wear a color when the point of the event is to meet people? Would you really feel that bad if your introduced yourself to someone who wasn't a "hacker?"
I know if feels awkward at first, but talking to strangers gets easier over time.
Having a "Hello" name tag looks kind of lame, but it really makes meetups a lot easier. If you donwload them, let me know. I'd be happy to email them to you.