What is the meaning of the different colored cassons? We saw a casson with black horses and the coffin drapped in a black cloth. We also saw a casson with the coffin covered with the flag and white horses.

Can't answer specifically about the colors, but you may be able to locate a contact from this page: The Old Guard - Caisson Platoon (http://www.army.mil/oldguard/specplt/caisson.htm)