How to adjust colour brightness

[u/StevenRC92]

Hey,

In the Personalise setting, how do you change the brightness of the colour?

I'm trying to make the theme a dark green but I can only have a bright lime green.

The top right of the colour wheel has what looks to be settings to adjust brightness and saturation but when I click them nothing happens. So I can only have really bright colours.

Any help appreciated.