When I installed my first HID's in one of my rigs, I was told to go with 6000K, and that they were the "brightest". I hated the damn things. They turned the snow on the road blue, hid black ice and gave me a friggin headache. I then moved to 4300K and everything looked clear, no blue or yellow tint whatsoever.
There is something to that. Water tends to scatter bluer light, while redder cuts through it. My RX-8 has Xeon bulbs, and I love how bright they look, but I'm in the process of swapping out the "white" fog lights for multi-tint, that are designed to actually cut through the fog (go figure) and rain.
