which wire is positive?

[scumdog]

Meh, that'd have worked. Actually I can't really see why they wouldn't work either way around anyway..

'Cos sometimes on the whole indicator housing (well non-plastic ones anyway) the earth wire is 'grounded' to the housing, not just to the side of the bulb.
Swap wires and you'll have direct short.

[sefer]

Ah, see that's what you get if you don't read the start of the post to discover it isn't just a standard bulb, plastic indicator

[Test Pilot]

get a test light and do it the proper way. Turn the ignition on and the indicator then test which one is flashing on and off with the test light. really simple really, you can also use a multi meter if you dont have a test light

[Test Pilot]

to tell which wire is which on the indicator just look for the wire that is attached to the housing is the earth, or more often than not the packaging usually tells you