I'm seeing the same bug with red headerbar buttons in other apps. I think colorhug-client was where I saw it last.
-- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to ubuntu-themes in Ubuntu. https://bugs.launchpad.net/bugs/1763417 Title: Thin red lines around red headerbar buttons Status in Ubuntu theme: New Status in ubuntu-themes package in Ubuntu: Confirmed Bug description: There are thin red lines around the format button of gnome-disks. Screenshot attached. ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: light-themes 16.10+18.04.20180328-0ubuntu1 ProcVersionSignature: Ubuntu 4.15.0-13.14-generic 4.15.10 Uname: Linux 4.15.0-13-generic x86_64 ApportVersion: 2.20.9-0ubuntu4 Architecture: amd64 CurrentDesktop: ubuntu:GNOME Date: Thu Apr 12 17:20:11 2018 InstallationDate: Installed on 2014-07-15 (1367 days ago) InstallationMedia: Ubuntu 14.10 "Utopic Unicorn" - Alpha amd64 (20140520) PackageArchitecture: all SourcePackage: ubuntu-themes UpgradeStatus: Upgraded to bionic on 2018-03-24 (19 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-themes/+bug/1763417/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp