Are there natural cold remedies for a nursing mother?

Rest, rest, rest: Not that you can get much rest while being a nursing mother, but i would take advantage of any available moment to sleep. I would also recommend tons of fluids and healthy foods. While their are no medications i generally recommend for colds, honey can help with a cough and warm drinks to soothe yourself.

Saline: I agree with Dr Wolfson's recommendations. I would add saline nose spray or use of a neti pot device with distilled water to help clean the nose out.