Colors on the viewport is a tricky thing. How they look like in the 3D view is altered a lot by the lighting in the scene. So you have to trust the values more than anything, because the visual feedback is not to be trust. It gets even worst when you have different color managements and Look up tables and stuff.
So what exactly do you mean that colors are not coming properly? Is it in the viewport? Also you can’t change the color in the mask, they always stay black and white.
