I’m currently working on getting my Hyprland/Noctalia setup looking the way I want. There is one nitpicky thing left that I cannot seem to find an answer to. How to change the blue accent/highlight color. This is the blue highlight that happens when selecting the text in Firefox’s URL bar, selecting a line in Filezilla, etc. Any suggestions of how to go about this as that blue, while nice, is rather jarring for my setup.
System wide theming is a constant issue but at least for the two applications you’ve mentioned you can focus on a single place. Firefox and Filezilla are both built with GTK3, so you should be able to find a stylesheet for it in ~/.config/gtk-3.0/.
If you’re using Noctalia’s GTK color schemes you might have a slightly different situation but it’s still the best place to start.
If i’m not mistaken, Noctalia shell autotheming sets the default GTK3 theme as adw-gtk (which has the blue highlight colors), without custom colors, as fallback for some apps, like the mozilla ones. I have solved this before by creating a link to the noctallia css in the user’s theme folder and, funnily enough, by setting said theme for Legacy Apps with gnome tweaks