Uh 4100k-4300 is the whitest white you'll get anything above that you'll start going blue and then purple. Stock/OEM/Factory HIDs on all cars come with 4100-4300K bulbs.
Does your dads allroad flicker blue? Its because of the cutoff on the lense not because fo the bulbs. If you look from inside onto the road the color is white. But if you look at it directly you'll see the blue flicker.
Mazda 3 hid projectors dont' give the best color on the cutoff but a couple peeps have swaped out their lense with clear lenses and used washers to modify the sheild to give alot more color at the cutoff.
Here some pictures.
Heres OEM Mazda 3 projectors with washer mod for more color:
OEM lens with washer mod and lens spacing done the sharpen the cutoff:
Valeo fresnel lens on the Mazda 3 HID projector with washer mod and lens spacing:
I borrowed those from Ruff so don't get mad if you see that man!
Heres a Evo8 lense swap on OEM Mazda 3 projectors borrowed from Say Chi Sin Lo.
Now heres mine i have s2000 projectors retrofitted onto my housings.
See you can have the best of both worlds best light output with 4100-4300k bulbs as well as plenty of color.
Anything else let me know.