[Affected versions]: - 63.0a1 (2018-08-23) - 62.0b19 build1 (20180820172315) [Affected platforms]: - Windows 10 x64 - Windows 7 x64 - Ubuntu 16.04 x64 - macOS 10.13.4 [Steps to reproduce]: 1. Launch Firefox 2. Go to about:preferences#home and set the "Homepage and new windows" to "Blank Page" 3. Click the Homepage button 4. Open a new window [Expected result]: - The Blank Page is successfully displayed in both Homepage and new window [Actual result]: - The Blank Page from the new window has a darker shade (light gray) than the one displayed in the Homepage (white) - See the following screenshot https://drive.google.com/file/d/16iWjpHdtKU7gRqEWF5IlrbawK7CcdIXz/view?usp=sharing [Regression range]: - I will provide the related details as soon as possible [Additional notes]: - The issue is most easily noticed on Windows and macOS platforms (less visible on Ubuntu) - Opening a new tab will fix the situation - The issue is noticeable on all default, light and dark themes

I somewhat suspect this might have the same cause as this issue: (In reply to :Gijs (he/him) from bug 1362774 comment #151) > *** besides a pre-existing issue with the 'blank' attribute not being > removed from the tab and the tab thus not rendering content that the user > inserts into the empty, null-principal'd about:blank document manually via > e.g. devtools or a bookmarklet. I'll file separately, doesn't seem urgent > given the STR. But I think I never filed the other bug...

Back with details regarding the regression window: - last good revision 5d86f27fe905246f8a3211da099f5e546315188b - first bad revision 0d93c364b753c9ecde20ab8e961bba61a9bb894d - pushlog https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=5d86f27fe905246f8a3211da099f5e546315188b&tochange=0d93c364b753c9ecde20ab8e961bba61a9bb894d - Bug 1379587 is a possible regressor