If it is only tinted pink but is still otherwise usable, it is probably just a sign that the display is suffering from burn-in or backlight bleed and is starting to fail. If it looks more like pink pixelated visual glitches it could be an issue with the RAM or the GPU. You could try performing a PRAM reset or reseating the RAM. If none of those tricks fix the issue, you likely have a failing display or GPU, in which case you would need to replace the failing part to resolve the issue.