What can I do about my dark gums?

Nothing. The color of your gums are genetic. You really can't do anything about this. Just focus on keeping your teeth healthy and your smile will look great.
Dark gums. Although most of the times it is pigment in the gums, if it just happened recently, you may want to make sure you are not taking in foods that have high lead content. High lead levels can cause bluish lines in the gums.
Nothing. Dark gums are usually pigment in the tissue. This is almost like a tattoo or having freckles. You really cannot change it.