Get a multi meter, unplug the lights. With everything unpluged, turn on the lights and push the prongs into the plug gently enough to make contact and not to destroy it. If it reads negative then the polarity is backwards, flip the nodes from the meter into the plug again, and if it's a positive number you've found which wire is positive and the other is negative.

Voila success.

Honestly, read the DIY i posted. its really straight forward and very easy to follow. Literally took me an hour for each side because I'm slow.

I'll be doing another write up maybe later this month for the fogs and the high beams (with DRL).

 

Yellow wire is positive, brown is ground.

 

Unfortunately mines are blue/black vs red/black.

Yesterday, the seller replaced the ballast set with another one. We have tested on the spot and they worked like a charm. This new set has got part on the one of the cables coming out from ballast and "HID ERROR CANCELLER" written on it. I have attached the picture. The old unit had similar parts. We thought that they were the cancellers which we learnt that they weren't.

So, long story short: I have been provided a wrong unit.

Thanks to everyone for their help effort. You guys are great as always.