KA1 color temperature

[LuckyL]

I remember the the first KA1 I received had a nice warm red tone when activating the natural light.
I had to make several returns and all the later readers seemed to have a more greenish tint and I put it down to different hardware batches, however, I recently had to reset the reader which reverts it back to the firmware version it shipped with. I noticed that the color temperature was red/warm as with my first device and after updating the firmware to 4.x, the greenish tint was back.

So it seems this is firmware related so I had a look at the .conf file and the only setting that seems to be related is "ColorSetting" which has a range from 1500 to 6500 and seems to determine the slider position in the light settings but not the base color temperature.

Has anyone else played with that and an idea if/how that can be set?