Birthmarks are skin blemishes that appear at the time of birth or right after. These stains vary in color from red, pink, brown, tan or blue. Usually these birthmarks are not dangerous. More than 1 in 10 babies have red vascular birthmarks that are made up of an increase in blood vessels. Almost all hemangiomas (red vascular birthmarks) disappear spontaneously by school age; however some require medical treatment.