Those who are born blind or become blind before the age of five do not see in their dreams. Nevertheless, their dreams are just as rich in narrative and detail as in sighted people. If one's sight is lost after the age of seven, dreams will still brim with visual imagery. A grey area exists between five and seven years.
Interestingly, those rapid eye movements (REMs) signifying that a dream is in progress do not occur, or occur very weakly, for those born blind or blinded before five.
How about congenitally deaf people? It appears that they may dream in sign language! Their dreams are also more colorful than those of people with normal hearing.
(Selsick, Hugh, and Baker, Fiona; "Dreamtime," New Scientist, p. 108, October 28, 2000.)