Mongolian spots are common in babies with Asian, African, Mediterranean, or Indian heritage. The bruise-colored marks appear most often on baby's bottom or back and usually fade by his first birthday. Strawberry marks appear on about 2 percent of babies. Sometimes the soft, raised marks don't turn red until an infant is a month old. Though they can grow bigger, take heart: Strawberry marks almost always disappear before a child reaches age 10.