Any of the HDD LED connectors from the case should work unless it is defective or polarity reversed. Colored wire generally goes on the + pin, the black or white other wire goes to ground (-) (but I've seen the LED connectors wired backwards too) - try it either way, won't hurt anything. Some HDDs have their own LED connectors so you can hook them direct if you have several. Which Antec case does he have that has three HDD LED pigtails?
.bh.