Shadows have appeared on the mobile screen, mostly from Facebook, what

Shades have appeared on the mobile screen and I don't know what the problem could be. When I bought it, they weren't there, but as soon as I installed Facebook, the shades of Facebook have appeared, and no other application has either.Shades have appeared on the mobile screen and I don't know what the problem could be. When I bought it, they weren't there, but as soon as I installed Facebook, the shades of Facebook have appeared, and no other application has either.