Hi,
I have seen many people facing this green screen issue, most of them are iPhone 13 series users. Here are some common fixes that worked for many iPhone 13 series users.
There are a couple of reasons you are facing this issue. 1. Due to Software glitches and 2. Malicious apps. You can resolve the green screen issue if it occurs for these two reasons, But if there is any physical damage, you need to contact Apple Support. Check out some common fixes:
1. Adjust display settings, Brightness level (Settings >>> Display & Brightness), Enable Auto-Brightness (Settings >>> Accessibility >>> Display & Text Size), Turn on True Tone (Settings >>> Display & Brightness)
2. Uninstall recently installed apps. Third-party apps could be the reason for the Green Screen issue on your iPhone.
3. Reset All Settings that will fix the minor software glitches.
Moreover, you can look into the post to see which solution works for you. Check this post for more fixes: https://www.igeeksblog.com/how-to-fix-iphone-green-screen-issue/
If nothing works, Contacting Apple Support would be the best choice.