I changed the GTK theme to Orchis-green-dark, I have an orange theme when pressing ctrl to find my pointer, or at this activities hot corner: 
And I want to make them green, like in Yaru-olive, but I want to use Orchis.
But if I change the setting to green in the settings app, it will reset the GTK theme.
31 Answer
I found the answer myself:
Install User Themes GNOME extension,
open gnome-tweaks change the Legacy applications entry to Orchis-green-dark,
and the Shell to Yaru-olive-dark. It was much easier than I thought!