Name Firefox Version 55.0a1 Build ID 20170519030205 Update Channel nightly User Agent Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:55.0) Gecko/20100101 Firefox/55.0 OS Windows_NT 6.1 Also to Note: This Window 7 (64bit OS) Laptop is using Microsoft's "Windows Classic" theme. On 2017-05-17, when I updated my Nightly, my 'Location bar' / 'Url Bar' now had a grey background. This looked very like the Screenshoot in Bug 1365789 "Incorrect background color for URL bar on Linux" Thomas Daede [:TD-Linux] on 2017-05-17 at 16:06:02 PDT posted this screenshot: https://bug1365789.bmoattachments.org/attachment.cgi?id=8868782 He fixed a typo: - --urlbar-background-color: moz-field; + --urlbar-background-color: -moz-field; I had hoped that this would 'fix my issue too'. Note: Bug 1365789 has been made DUPLICATE of Bug 1365275 "Location and search bars become transparent on hover with a lightweight theme installed" On 2017-05-18, when I updated Nightly, this was still not fixed (in my case). I used Build ID 20170518030213 on a new Profile. The background is still grey (in both URL Bar and the Search Bar). Seen on First Run. See Screenshot "Windows-Nightly-x64-2017-05-18-First-Run-on-New-Profile.png". https://bug1365789.bmoattachments.org/attachment.cgi?id=8869075 I wonder if, in my case the "Windows Classic" theme (from the OS), is a significant factor. See also Bug 1363122: "Widgets are not correctly drawn in Windows Classic theme since asynchronous flush rendering has been enabled" I have created another new profile. See Screenshot "Windows-Nightly-x64-2017-05-19-First-Run-on-New-Profile.png". Still 'grey background'. Also the identity-box 'looks wrong', has a grey background too. The font size, used for the URL, is 'back to normal' (fixed in BUG 1365906). Here is a recent Screenshot (2017-05-17 - from another bug - not my PC) that 'looks OK to me' (for the background color of the URL and Search). https://bug1365256.bmoattachments.org/attachment.cgi?id=8868641 DJ-Leith

Windows-Nightly-x64-2017-05-19-First-Run-on-New-Profile.png