3000K has an approximately 3200lm output, which is more than 3x the light output of the traditional halogen light. 3000K emits GOLDEN YELLOW color and offers superior penetration power during adverse weather epically in dense fog. The applications of the 3000K kit aim more towards secondary lighting apparatus such as high beam and fog lights. The 3000K capsule is actually a 5000K capsule specially coated with a film that filters out all the wave length except the range of wave length which emits yellow. This is the color temperature that will catch all the attention on the road.
4300K has an approximately 3400lm output, which is more than 3x the light output of the traditional halogen light and is the color temperature with the most output. The light appears fairly white, and has light yellowish hue when reflected off the road identical to the OEM HID equipped vehicles. This color is for customers who is looking for pure performance white improving the looks of their headlight. It is idea for customers who does a lot of back road or canyon driving and need the optimal visibility. This is the color temperature that give you the most light for your money. This is akin to "creamy white".
6000K has an approximately 2800lm output, which is 3x the light output of the traditional halogen light and slightly less light output compared to the 5000K. Although it has a bit lesser light output, it emits pure whiter light with very slight and barely noticeable tint of blue and purple. Think of this as a "stark white".
8000K has an approximately 2550lm output, which is about 3x the light output of the traditional halogen light and slightly less light output compared to the 6000K. While it has a bit lesser light output, it emits bluer light than the 6000K
10000K has an approximately 2200lm output, which is more than 2x the light output of the traditional halogen light. 10000K produces a deep blue light output approaching violet and the blue is noticeably deeper than the 8000K.
12000K has an approximately 2100lm output, which is more than 2x the light output of the traditional halogen light. This color temperature puts out a deep bluish violet light and is deeper colored than the 10000K. It is for customer who is looking for the most extreme and most exotic looking light output.
All HID vary due to power and a bit of a color difference. Most kits with the same "K" will look almost exactly the same to the naked eye.
Please note that "K" references vary from manufacturer to manufacturer. There is no specific quality control when ordering anything other than 4300K (OEM). As such, the 6000K we receive from our manufacturer is closer to 5000K of most other manufacturer's kits. That is, our 6000K is more stark white than blue (per our customers comments).
Some excerpts from: newtiburon.com/forums/showthread.php?t=151424