Just got rid of the problem. I have got Philips 43PUS6501 and NVidia GT 730 2GB DDR5, both running on 4k/UHD. Everything was OK, except some yellow glow around text on white background (Clear Type turned off).
It's because the nVidia to run on 60Hz, forces output to CROMA 4:2:0, and that greatly impacts text sharpness. Lack of color depth can lead to muddy text on certain backgrounds. Switching to 30Hz on old HDMI cable turns down the amount of data that is sent over the cable by half. Remember, that running 4K/UHD@60Hz at 4:4:4 uses over 12Gbits of transfer, and the old HDMI cables run max 10.1Gbit.
The problem is that I have some old HDMI cable, it's v.1.4, but now the HDMI V.2.0 Cable is on it's way. :) Till then I set refresh rate in nVidia Control Panel from 60Hz to 30 Hz, and the glow is gone.