The tan cable (back light) is damaged within the display assembly. This is not repairable, you will need a new display assembly [https://www.thebookyard.com/product.php?products_id=20096|11” MacBook Air Display Assembly (Used Grade-C) Apple P/N 661-6624] finding this part is getting hard! This is one of the few places which has it. Given the age of the system I wouldn’t spend much more here, Here’s the guide to put it in [guide|12341]