(~4500K) but saw no indications when viewed with the LEDs (~6500K). None of us really thought of performing that test, fortunately our QA/CWI manager is a borderline genius. Scrapped all the LEDs after that.
The jump to 6500K put the light well into the blue spectrum.
I personally wouldn't use anything outside of the 5000-6000K range, as this is the best red/blue mix for the whitest light for driving, but will still distort color reflection.
All retail chains use 4000 - 4400K lighting for displays, as this is the closest to sunlight, and doesn't distort the color of the reflected light off the items in display.
HID and Halogen were the choice for decades, but the actual main purpose of all those types, including all incandescent, is to generate heat, and light is just a byproduct.
We are paying for that wasted heat to be generated with every lamp, even LED's, as a diode can only pass DC, so AC has to be filtered with a rectifier and ripple cap, with heat loss during every change of state of the energy.
There's much less energy loss with LED's.
There's a cult of folks that perhaps think the higher intensity the better, but I disagree.
The high frequencies of 6000 and up will bounce and reflect off the airborne water droplets in fog, rain, or snow, which can blind the driver.
Clear night driving will see a further reach of blue, but all around driving that will be adequate for most conditions needs to be a lower kelvin rating.
Some folks also like to refer to the Doppler Effect as their justification, but that really only manifests in sound here on earth for our purposes in this discussion.
It reminds me of the ECM.
Manufacturers set the parameters to handle most conditions, which means we will then use tuners to get best towing, a different tune for freeway mileage, one for 1/4 mile run, etc.
Unless I'm going to install a couple different banks of lights to match the different conditions I'll stick with an all around temperature and not overdrive my lighting.