How can I change the background of pix image viewer from grey to black?

[aljustiet]

How can I do that?

I want the grey area around the image to be black. I searched it in the settings, but couldn't find.
OS: Arch

[Jopp-gh]

In Pix you can't change app colors.
Open Mint's settings>themes instead. In there, click on the Advanced button, to configure the user interface.
You should be able to change from a dark grey to black.
Otherwise, try to download other themes (another tab under themes).

Finally, to modify some specific colors check out: https://www.dedoimedo.com/computers/linux-mint-cinnamon-edit-theme.HTML
But it's more advanced.