Chosen Solution
Yellow square is 2 inches from left and about 2 inches wide. External monitor connection is OK. Can still see screen contents but discolored.
You have a TAB fault in your LCD. The LCD is not repairable, it needs replaced. You should be able to find a LCD on eBay for your model. The replacement instructions are in the service/hardware manual. You can get the service/hardware manual from HP the support web site. You didn’t give your model number or I would have provided a link to it.
