How to change one aspect of the default theme?

[nikgnomic]

Another user reported a similar issue with thunar gtk3.0 theme recently. Their solution was to create a CSS snippet in home folder to change one CSS selector

@jamjar

Put the following line into ~/.config/gtk-3.0/gtk.css (create it if it does not exist).

@define-color theme_unfocused_selected_bg_color #555555;

–substituting obviously the color you want for #555555.