How can i fade a mongolian spot?

Be patient: Mongolian spots fade by themselves over the years. If they are deep and dark at birth it may take until the teen years(as it did in my son's case, who looked like somebody had poured a bottle of blue ink on his back at birth!). Just don't pay attention to it and don't make the child be self-conscious about it. If it is a highly visible place, i suppose you can apply some cover up cream...