I've used regular Sharpie magic markers on Countryman B3, +1 to Colin's comments. Don't worry about not being able to clean the stain off the mics ... you will never want them the original color anyway.
Fyi if you are purchasing new mics I would suggest dark brown color only, for actors of any complexion. Anything lighter shines too bright, and black is just too contrasty against skin no matter how dark. The dark brown looks more like a strand of hair when coming down from the hairline.