Most of the programs with a graphical interface out there come with a light theme by default. Unfortunately I'm the kind of user that likes their screen more dimmed. On mobile devices one is often lucky and there is a dark theme waiting to be used. And also on my machine running Arch Linux I managed for most tools to come with a dimmed ui.
I do use pulseaudio as audio deamon and therefore pavucontrol to manage the volume of the various audio streams. Now pavucontrol uses GTK3 to draw their ui. To get pavucontrol with a darker ui one must look for GTK3 themes.
The following describes the steps to be taken, to change the theme to `Arc-Dark`.
Download the latest snapshot into your tmp folder and extract the tarball.
Build the pacman package and install it
For Changing GTK2 Themes
The tool gtk-chtheme can be used, to change themes for GTK2 applications. I first had the impression that pavucontrol was using GTK2. This is actual wrong, it is using GTK3. Anyhow it might be a good idea to change the theme for both. gtk-chtheme is available within standard arch repositories.
For Changing GTK3 Themes
The tool lxappearance is able to change GTK3 themes and it is also available via standard arch repositories.
Changing the Theme
Themes are actually changed pretty straight forward. Within gtk-chtheme one is presented with a window where one can choose the theme from.
And also lxappearance is asking on the main screen for the theme to choose.