Although most tartans have no symbolism to their color scheme, this is not always the case.

Maybe I will be corrected here, but the story that I've heard about the black Douglas tartan does have meaning in the tartan's colors. Something along the lines that the name, Douglas, was derived from the name of the land, which was named for the black (dubh) water (glas) in the land. And that's why the original tartan is done in black.