8K vs 6K
Here are some more examples of the difference between 8K vs 6K HID's. I personally prefer the whiter look of 6K. Stock is around 4.2K (yellowish). My personal car (under signature) has the 6K's which I specified when ordering otherwise you will get 8K.
2015 BMW F10 M5, Space Gray, Dinan Stage 1 Engine, Exhaust, Coil Over Suspension, Sway Bars, Vorsteiner Staggered 9 /10.5 '20's, Custom Coded.