Chosen Solution
I just replaced my screen using one of ifixits screens and guides and the colors just seem off. They dont seem bland or dull, they just seem different. Also, maybe its just me being aware of it but everything seems crisper (i know thats a good thing but its still not normal and im wondering if there is anything wrong.)
Disconnect the battery, and try to re-seat the screen connectors. If that doesn’t change anything, then try your original screen to see if the problem is consistent with your new screen or phone. If your replacement screen continues to show off colours, contact iFixit support for a replacement.
Agree with Minho however a good thing to check is Night Shift is off as this will change the appearance of the display.
On the majority of the cases, the new screen has slightly different colors. This was the case in many replacement screens, even original ones. If the difference is big, then you must seek for a replacement
