Black and white in paint mod don't react the same

Support Materials and Textures
9

here you can download the latest Blender version

edit,
I have made a test with 2.90 alpha version.

i added a basecolor texture to the cube,then i switched the color in the brush settings to black and just draw.It became pure black (0,0,0) on the texture.then i switched to white and draw,get full white 1,1,1.

Then i switched the color back to black and reduced the strength down,and painted a few strokes untill it becames black again.

I think this works as it should.

paint
paint1915×1132 132 KB

Keep in mind,that if you reduce the strength down to 0.047,then you need around 22 strokes to get the full opaqe color you have selected as brush color.(1/0.047).Reduce the strength simulates how strong the brush stroke of the selected color is (opacity),and not reduced color value.