My daughter dropped my trusty 2013 15 inch MacPro retina. The bottom 1/8 of screen is now psychedelic. Sounds like a screen replacement or laptop replacement time, but I thought I'd drop in here to see if there was anything simple I missed.
No, I think you have the right idea -- rainbow colors, particularly if they are radiating from one area on the screen, most likely means that that LCD screen is cracked.
Nothing you can do except replace the panel (or decide if replacement is worth the cost on a 7-year-old laptop (?)
Yeah thanks, Five years ago she needed a workhorse laptop. Now maybe not so much, but I suggested that she take a close look at the the new 16 inch model, or the newly released MacBook Air, or possibly the new iPad Pro that will have trackpad support. All very different machines. I usually suggest that they swing by the apple store to check them out, but alas the stores are closed now.