The "K" for instance in "8000K" represents the certain bulb color temperature output, and it's the abbreviation for the word Kelvin. Below is a chart showing you the range of the Kelvin temperatures. Lower Kelvin temperature will emit a more red output. The normal halogen lamp color temperature is rated at 3200K.
Many first generation Factory equipped Xenon headlights emit 4300K, because the color temperature output gives out more usable lumen. Most second generation Factory Xenon headlight sets use 6000K to match the output for some LED Daytime Running Lights. 6000K is a representation of the Sunlight's light, which is pure white. The higher the Kelvin temperature, the output becomes more bluish to purplish.
It is normal to have the output more blue when the HID Bulb first come on. The first 30 - 60 seconds is the HID's loading phase. The color temperature of the HID Bulb should adjust to its rated output after the HID loading phase.