I just had the same problem on my K95. No setting for 255-255-255 (or ffffff) would get "white" on the KB.
It looked an off-white/turquoise.
When someone said "it doesn't look white like my lock heys", I tried something.
I hit the manual brightness key.
The brighter I switched it to, the less blue it looked.
NOW it still has a slight tint to it, but it doesn't look as bad. I may want to experiment and see what turning down the blue alone will do...