Forever on the search for “The Right Tool For The Job” * – the “right tool” for color mixing / blending / painting is Krita.
Despite warnings that it *might* crash when used with my old built-in laptop card, it works perfectly fine. [i tried several colors and blenders, then ran it through something called “gradient filter” which seems to pick pleasing combinations of colors]
So, should I ever take up painting, this is the tool I’d use.