The colors of the clothes that medieval nuns would wear were usually a white-grey, or black. The white-grey color was due to
un-dyed wool, early nuns wore their habits like this. A habit is the name for the clothes that nuns wore. Some nuns wore their habit
un-dyed, to show the life of poverty. Later, the colors would typically be black. They would wear a wimple and a veil that was attached to their scapula. A scapula is worn over the shoulders with an opening for the head, it is made out of a large piece of woolen cloth. They also wore a habit, which was tied around the waist with a belt made of leather or cloth. Monks would wear clothing of similarity to the nuns, except instead of a wimple and veil, they would wear a hood that was attached to the scapula called a cowl.
here is a picture of a medieval nun with an
un-dyed habit.
http://www.englishare.net/literature/guinevere-nun.jpg
here is a picture of a medieval monk
http://images.buycostumes.com/mgen/merchandiser/19047.jpg