Green vertical lines across bottom half of Onn TV

Does the TV do that on other things, such as while using a DVD or antenna?  How old is the TV?  You could try unplugging the TV from power for at least a couple of minutes and see if that works or try a factory reset.    It is possible that the TV panel has gone bad or the control board inside has gone bad, which happens pretty frequently with certain budget level TV brands.  Since it is an Onn brand, you should also reach out to Onn technical support.