The coloured wires are positive... but if ya can't get it going, just turn the connector around and put it on the other way around. This will not harm the board at all. The pos & neg conecters only matter for your leds (power & HDD), not the switches. The switches/ butons are just momentry switches (the just close a circut), so therefore have no pos or neg wire... the circut is just either open (button not pushed) or closed (button pushed).
As far as your power led connector not being the right size, it doesn't matter... just cut the connector in half, shaving the connectors plastic so as it will fit. The main thing is as long as the coloured power led wire is connected to pin 1 on the motherboard power led connection...
See..... Clear as mud...
If I can help any further, gimme a yell,
Smit