paint.net 5.0 dropped support for Windows 7, however, when you have a high contrast theme enabled, the message telling you that you cannot change the theme still mentions the Classic Theme.
Of course, with Windows 7 support being dropped, paint.net does not support any operating system which lets users use the Classic Theme. Now, of course, there are people on Windows 10 that use the Classic Theme, unofficially. However, I believe it would be best to remove the mention of Classic Theme in the options.
