iMac 4K uniformity problem

Hi,

I tested new iMac 21.5 4K with Retina two days and I noticed a problem with uniformity of backlight.

When I read a text from the screen I feel that some parts of text has a slight reddish tint of background and other parts has slight greenish tint. If I move my head these redish and green areas are moving also. If I show a white picture on the entire screen this problem also can be ovserved. The color difference of white baclground is very small and it's hard to see. But when I read text and scroll the page I can easily feel that background has different tints. It's really annouying problem.

I wanted to buy new iMac 4K and now I don't know - is this problem common for all iMac 4K or only for certain Macs.

I've read that new iMac 4K has a new backlight with a set of LED with red and green luminophore. Probably here is the problem? A poor mixing of light from different LEDs.

This problem don't happen with old iMac 21.5 or my Macbook 12 which have traditional backlight with LED with yellow luminophore.