What Causes Blue Coloured Hands?

my 15 yr. old daughter's hands (fingers and the side of her right hand palm) turn blue randomly. not always in an a/c climate) lasts from an hr. to the latest 5 hrs. this just began beg. of july and episodes seem to be getting more intense (deeper blue & latest with blue stripes on hands) and last longer. saw a rhuematologist and he claims he never saw this before. (the turqouise color she gets on the side of her rt. palm)