The other method is to rip off your matching shirt before the other person notices and sprint away.  But then, you do run the risk of the other person doing the same thing and now, there are two people running around without shirts on.  Double awkward.

↓ Transcript
man 1: that guy over there... he's also wearing this shirt!

man 1 (thinking): he notices too...
man 2: what the... really?
man 1: yup, this is happening

man 1: listen, dude, no one can see this.
man 2: oh no! people are coming!

man 1: ok, you run that way as fast as you can! i'll do the same, but in this direction!

man 2: one, two, three, GO!
man 1: don't look back!
man 2: faster!

man 1 and man 2 (both thinking, looking back with sad faces): in another life, we would have been the best of friends...