It is using a system color picker. That’s the gtk color picker. You’d need to configure xdg-portal to utilize a different picker I’m pretty sure.
https://wiki.archlinux.org/title/XDG_Desktop_Portal might point you in the direction you’re looking for… Not 100% on this though… maybe switch from portal-gtk to portal-kde?
One of the biggest downsides of a VPN; you share an exit node with lots of other people, only takes one bad actor to get your exit node ip banned