In order to edit the look of the majority of things I use which are based in Gtk 2.0, I use a program called LXAppearance.
It’s available on the community repos so you don’t need to go look for it in aur.
sudo pacman -S lxappearance
in the terminal and you’re done.
This program can manage themes, colours, icons, mouse cursor, fonts and some other extras and it’s really really useful.
That’s it for now – once I find out how to edit Qt stuff I’ll be back on this :)