Blue shadows on replacement screen

Hello all,
After taking my time to replace the display, which I cracked, I managed to get it done the other day. It was pretty straightforward, especially after doing it once. However, I notice a couple of, what looks like, blue shadows on the display. They can really only be seen with a white background but as I know they are there, I see them, if that makes sense.
Has anyone else found this? I have tried ensuring that the cable is in correctly and it seems to be.
Many thanks