I am becoming quite adept at using gimp but i'm still learning. When using pencil brush or airbrush by changing the mode from normal to hue or color I am able to change a color to another without losing any texture or detail. The problem that I am having with this is that I cannot do this method with black or white, while trying to use either it only paints over the previous with gray. I will try to add a photo example to show what it is i'm talking about.
The top line is done with red in color mode. The middle line is done with red in hue mode. The bottom area is black in color mode and black on hue mode has no effect. I would greatly appreciate any tips that would help me with what I am wanting to achieve.