Created attachment 9425 Light Highlight color Mousepad's "Classic" Theme changes according to System Theme. However, Line Highlight color is fixed. Is there any way that these colors can be changed by users or changes on theme change (Thunar's Highlighting seems to have a better job than mousepad by showing darker color on item name background on light theme and showing lighter color on item name background on dark theme). I use Adapta-Nokto-Maia and Adapta-Maia.
GtkSourceView handles the styling and also provides the "Classic" theme, see: https://gitlab.gnome.org/GNOME/gtksourceview/blob/master/data/styles/classic.xml Your issue was reported here: https://gitlab.gnome.org/GNOME/gtksourceview/issues/29