If one of these versions of Windows is detected in Edge 94+/Chrome 95+, or matching versions of Opera it will turn red.
This will also be able to tell if it is running on an older version of Windows (7 to 8.1) or a non-windows OS.

Not Windows
Windows < 10
Windows 10
Windows 11

Microsoft Source: https://docs.microsoft.com/en-us/microsoft-edge/web-platform/how-to-detect-win11

Class injection test by Jeff Clayton

Test Site 1: https://browserstrangeness.github.io
Test Site 2: https://browserstrangeness.bitbucket.io