Ubuntu – Ubuntu 18.04: Change color of window title bar

Have you checked the answer for this question? Create or edit ~/.config/gtk-3.0/gtk.css as:

.titlebar {
    background: #3089FF;
    color:white; 
}

.titlebar:backdrop  {
    background: #777777;
    color:white;
} 

Note that you can choose different colors to suite your preferences. Then refresh the gnome:

setsid gnome-shell --replace

I just tried it and it worked for me.

I was able to add border to windows in Ubuntu 18.04 by doing the following:

nano ~/.config/gtk-3.0/gtk.css

Then add the following:

decoration {
    border: 3px solid gray;
    background: gray;
}

After saving the file, remember refresh gnome using this command:

setsid gnome-shell --replace

I found it works well for Ambiance. I like the border slightly thicker (3px) to make it a little easier to see in laptop running in 1920x1080 resolution.

EDIT:

To customize the active title bar background colors. (use :backdrop for inactive windows)

.titlebar {
    background: #0759EB;
}

.titlebar:backdrop  {
    background: #829EDF;
    color:white;
}