I have a multi-colored mole what should I do?

See your derm. Remember your abcd's when thinking of melanoma. Look for moles with asymmetry boarders that are irregular color differences within the same mole diameter greater than 6mm also any new mole or old that starts to itch, bleed or ulcerate should be of concern. Another rule is the ugly duckling rule. Which refers to a mole that looks distantly different from the others on your body.
See a dermatologist. Moles can come in all different colors and doesn't necessarily mean it's dangerous. Color variations and multiple colors might be a sign of melanoma so you should definitely have that mole looked at by a dermatologist. It may require a biopsy.