5s Screen lost colour, seems mirky, less vivid

Hi everybody

just a couple hours ago I was using my iPhone 5s, turn of the screen then back in like 10 seconds later and noticed that the colours seemed different to what they were just before, less vivid. The colours seemed to have faded and the image has become "mirky", a white tint. Very noticeable the greens of the phone and whatsapp icon are less vivid. (see attached picture)
At first I thought it was just my eyes messing with me as I was in some weird light but when I got home I compared it to my iPhone 5 (black) and the colours are indeed different.
A couple days ago I compared the two and the colours seemed identical.

I thought the screen was broken so I replaced it with the screen of a 5s that had a broken logic board. But the colours remained the same. So it is not a defective screen.

So my question is, has anyone ever seen this happen before and what could be the cause? Software or Hardware, both?

thanks in advance

Supermallet said:

Isn't there a dimming setting in the Accessibility section? Maybe that got triggered somehow.

Click to expand...

thank you for your reply
The first thing I did was look through the accessibility settings and everthing was off or not adjusted. Reduce white point is off and turning on darken colours does not help.
ill try a restore laterbut quite certain its not software

-- It was just really bad for like 1 min. It became really hazy, like looking through fog at the screen, it went away just as I was going to take a picture --

-- a restore hasn't changed anything --

Does anyone else have any ideas.
could the gpu be an issue, logic blard connector?

cheers