HID Bulbs & Colors
4300K is the color temperature used by most vehicle manufacturers because it produces the most visible light with the least heat (highest efficiency).
With separate High & Low bulbs, the lows CAN be wired to stay on with the highs; with HID, the lows SHOULD be wired to stay on. A simple jumper across the dimmer switch (from input to low) will do that.
Low Beam - H7
Hi Beam - H1
See also: