Big Sur - how to stop the top title bar from continually changing colours

I just upgraded to Big Sur and the top title bar is continually changing colours. That is so distracting. I'd like to go back to whatever the old one was. I think it was black text on a clear top titlebar. I don't like white text on a coloured background either. Is there a way to change it back to a basic black text on a light background ? I don't like being forced to have these rotating colours up there ! Purple, brown, blue, chartreuse, green, reddish, clear with black ! Seriously !? Help !

Mac Mini.