When I'm painting (in 3.6), the colour works fine until I add the texture, then the colour changes to black no matter what I pick. If I disable the texture, it goes back to painting in my selected colour, but then I can't use the texture.
I couldn't find anything on google except for this and this, and those solutions didn't work for me.
I also tried enabling and disabling a whole bunch of random options, and it didn't change anything.