I just updated to the latest Version 7 SR17(7.17.22102.5001, 2022-04-12)
When I try to add another glow color to the glow post effects by clicking the plus icon, Rhino keeps adding color slots.
This happens both in the post effects panel after a Rendering and in the Options render settings.
Luckly or weirdly I can exit the dialog. Any kind of trying to uncheck the added color dialogs makes Rhino add even more slots instead of disabling.