HID bulb colors are measured by their Kelvin temperature. HID bulb light output is rated by its luminosity or lumens. OEM auto manufacturers use 4300k bulbs for their high luminosity output (generally 3200-3400 lumens) and their reliability.
A variety of places sell the 8000k & 10,000k bulbs (and even higher). These bulbs have a low true lumen/output rating, produce obnoxious glare to oncoming drivers & cause eye fatigue on you the driver. Often times these aftermarket bulbs don’t produce anymore output than a quality halogen bulb. 4300k-4500k is the brightest and truest white HID bulb you can get.
The only other color bulbs that SuperDutyHeadlights.com would use in a retrofit are 5000k, 5500k, 6000k or 6500k bulbs, and we usually reserve these strictly for users that want specific Kelvin coloring.