Dominican friars, nuns and sisters are unique in wearing a white habit, as many other religious orders chose brown, grey or black for their clothing.
White is certainly not a practical color (considering how easily it can get stained), and was chosen by St. Dominic for its connection to a legendary dream.
According to Aleteia's Fr. Patrick Briscoe in his book Saint Dominic's Way of Life, published by Our Sunday Visitor, St. Dominic originally didn't have a distinctive habit.
St. Dominic soon changed the newly established order's habit after a miraculous vision.
This happened when a newly admitted member, St. Reginald of Orleans, became seriously ill.
St. Dominic prayed to God for a miraculous healing, and soon after St. Reginald regained his full health.
Afterwards, St. Reginald told St. Dominic a vision he witnessed, as narrated by the early 20th-century book Short Lives of the Dominican Saints.
St. Dominic then announced they would exchange the white surplice for the white scapular given to them by Our Lady.
This story is commemorated each time a Dominican friar or nun receives the habit.
The white scapular then is a constant reminder of the Dominicans' devotion to Our Lady, as well as to challenge them to a life of purity.
