6000 low beam and 4300 high beam here
Colors:
Color is important, 4-5k gives the best performance and is closest to natural sunlight. It is also far less offensive to the eye, yours and oncoming traffic. The higher temps are more for bling factor, but will give less light and more "glare".
3000K has an approximate 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.
4300K has an approximate 3200lm 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 are looking for pure performance white improving the looks of their headlight. It is ideal for customers who do a lot of back road or canyon driving and need the optimal visibility.
6000K has an approximate 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 less light output, it emits pure whiter light with very slight and barely noticeable tint of blue.
8000K has an approximate 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.
One word of warning is you do not want to use the 4300 for your low beam. It puts out the same color of light as the sun and is not visible to other drivers if you are between them and it when it is rising or setting.