Preflight Checklist

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a feature request that matches the one I want to file, without success.

Electron Version

14.0.0-beta.11

What operating system are you using?

Windows

Operating System Version

Windows 10 21H1, macOS 11.5.1

What arch are you using?

x64

Last Known Working Electron version

14.0.0-beta.10

Expected Behavior

Creating a BrowserWindow with the backgroundColor option results in the new window displaying that color behind the transparent WebContents.

Actual Behavior

Creating a BrowserWindow with the backgroundColor option results in the new window displaying a white background color behind the transparent WebContents.

Testcase Gist URL

https://gist.github.com/4256f388d41ef0d974645a11ab72b1fe

Additional Information

The problematic version was discovered using Electron Fiddle's bisect feature.
v14.0.0-beta.10...v14.0.0-beta.11

#30136 seems related

I'm not seeing this behavior in a testing build of current main (8007d01).

I'm looking into a fix, will update as progress is made.