I use KDE Plasma, and much prefer the KDE color picker over the GTK one that Firefox uses, with input type=color.
I know that I can set GTK_USE_PORTAL=1 to make Firefox use the native file picker, is there a way to make it use the native color picker as well?
I know there probably isn't a way, but I figured it's worth a shot asking.
No. The purpose of Linux is to provide a free and open source operating system, that can be customised by yourself and the community to your liking.
I like KDE's colour picker. It seems I would like the Windows one as well. It's a good design. Linux doesn't exist to be contrary, it exists to be a customisable, open experience.