I have Kubuntu 18.04 fully updated in VirtualBox.
I copied the Breeze Dark folder from /usr/share/themes to ~/.themes and renamed it to My-Breeze-Dark. Then, I made changes to ~/.themes/My-Breeze-Dark/gtk-3.0/gtk.css. I changed every occurrence of #eff0f1 to #ff00ff. There were 124 replacements. (I tried more sober colors as well.)
Then, in System Settings > Application Style > GNOME Application Style, I chose My-Breeze-Dark and clicked Apply. When I opened gtk3 applications such as Firefox or Google Chrome or gnome-screenshot, no text was colored #ff00ff.
I even rebooted and checked. No difference.
Then, I backed up the original Breeze Dark folder and modified /usr/share/themes/Breeze-Dark/gtk-3.0/gtk.css. I used System Settings > Application Style > GNOME Application Style to select the system theme. Still no change. I even tried checking/unchecking "Prefer Dark Themes". No difference.
What is the reason? I can make whatever changes I like in ~/.themes in 16.04 but apparently not in 18.04
Minor issue: why are there folders for 3.18 and 3.20 when 18.04 will be using gtk 3.22?
I copied the Breeze Dark folder from /usr/share/themes to ~/.themes and renamed it to My-Breeze-Dark. Then, I made changes to ~/.themes/My-Breeze-Dark/gtk-3.0/gtk.css. I changed every occurrence of #eff0f1 to #ff00ff. There were 124 replacements. (I tried more sober colors as well.)
Then, in System Settings > Application Style > GNOME Application Style, I chose My-Breeze-Dark and clicked Apply. When I opened gtk3 applications such as Firefox or Google Chrome or gnome-screenshot, no text was colored #ff00ff.
I even rebooted and checked. No difference.
Then, I backed up the original Breeze Dark folder and modified /usr/share/themes/Breeze-Dark/gtk-3.0/gtk.css. I used System Settings > Application Style > GNOME Application Style to select the system theme. Still no change. I even tried checking/unchecking "Prefer Dark Themes". No difference.
What is the reason? I can make whatever changes I like in ~/.themes in 16.04 but apparently not in 18.04
Minor issue: why are there folders for 3.18 and 3.20 when 18.04 will be using gtk 3.22?