Is by any chance this monitor delivered to Greece? I guess we have a defective batch if that's the case. Mine was made on Sep 2020. The feeling was like this: The white color looked REALLY weird, exactly as you describe, like a moire interference (check moire interference patterns and you'll understand), even with brightness at 0% and eye distance from the monitor of an arm's length. Dizziness in about 20-30 minutes, very heavy head, and for god's shake, it gave me a terrible nauseating vertigo, and imprisoned me in my room for 3 days straight without lights nor sound as I developed photophobia and phonophobia. Needless to say, I was really afraid of the monitor, and immediately returned it to Dell. Imagine getting a new monitor to help you with extended screen usage (like programming and gaming) and instead get ocular migraine, dizziness and nausea.
edit: Also, thank god there is another person that feels this, I thought I was going crazy. And since it's a common problem, they will certainly accept a return. I don't think they want to be responsible for health issues, these should not be taken lightly. To us it was just an eye strain and vertigo, on someone else it might trigger some epileptic seizure!