Screen is too blue

Lenovo T520 running Windows 10 pro. It's not the Blue Screen of Death, it's that areas that should be white are blue, and the resolution is poor. Periodically corrects itself for an hour or 2. This has happened before, and preceded a hard drive crash during a system update. Following the crash,the hard drive can't be recognized and has to be formatted. The second time, I replaced the hard drive but it didn't solve the screen problem and again crashed on updating. That time I restored to Windows 7 with the factory recovery disks. It hasn't crashed yet (3 days) but the screen is still too blue most of the time. It passes all the diagnostic tests except the one where the screen should be all white (it's blue). The problem is present on the splash screen when booting up, which I'm told means a hardware issue. I've read that for people with desktop systems this problem is sometimes the cable. So finally the question: should I open up the laptop and mess with the cable? Any other ideas?

Thanks a lot!

So I removed the LCD screen and, obviously, detached that end of the cable, and I've exposed the other end of the cable, but I'm not sure how to detach it. Does it just slide out the screen end, or do I have to release some clip or something? Please see photo. Thanks!

It works! I cleaned both ends of the cable and both connectors, put it back together and it booted up normally. It's been fine all day and I think it would have reverted to blue by now if it was going too. Many thanks!