[WuNgUnSVT]

My advice...stay away from any colour temps above 4100K
ALL, and I mean ALL OEM HID applications use just 2 bulbs...the Philips and the Osram, and always 4100K.
The colour shift you see if from the projector lens, as the light is refracted near the edge of the lens, and by the cut-off shield. It has NOTHING to do with the colour temp...
And if your gonna 'convert' your halogen housing for an HID bulb, your gonna get flashed alot...and if you wanna aim your headlights so low as to prevent this, then the HID's aren't gonna perform as well as the OEM halogens...and I would NOT use anything other than Philips or Osram bulbs, period!
I'm getting Ebay 'KS' dual halo projectors, yanking out the projector assembly, and dropping in some OEM (Audi A6) Valeo projectors/ballasts and Philips 'bulbs' from hidplanet.com
This will look and perform awesome!!