There are a few different things that could cause your TV screen to go green. One possibility is that your TV is connected to an AV receiver or sound bar that's set to the wrong input. If you have multiple devices connected to your TV, make sure that the AV receiver or sound bar is set to the correct input.
Another possibility is that your HDMI cable is loose or damaged. Check all of the connections between your devices and make sure that they're secure. If you're using an older HDMI cable, it's possible that it's not compatible with your newer TV or other devices. Try using a different HDMI cable if you have one available.
If neither of those solutions work, there may be something wrong with your TV itself. Try power cycling your TV (unplugging it from the power outlet and then plugging it back in) and see if that fixes the problem. If not, you may need to contact customer support for your specific TV model for further troubleshooting assistance.