The Marine Corps' Male Officer Blue Dress Uniform comes in four alphabetically desig-nated variants, “A” through “D,” with the “C” and “D” versions replacing the Dress Coat with a long-sleeved shirt and tie and an open-collar short-sleeved khaki shirt, respectively. But while all four versions may be prescribed for parades and ceremonies, only the “A” and “B” versions (as well as the “A” and “B” versions of the Blue-White Dress Uniform for SNCOs and Officers) may be worn during official visits involving civil officials, officers of the U.S. Armed forces, and officials or officers of foreign governments.
Other occasions calling for the wear of the “A” and “B” Blue/Blue-White Dress Uniforms include receptions given by or in honor of officials or officers (see Chapter 12 of U.S. Navy regulations), daytime formal or semi-formal events, and parades, ceremonies solemnities, reviews, and entertainments when the Commander or Senior Officer wishes to pay special honors.
The only difference between the two Blue Dress Uniforms variants is that large ribbons are worn with the “A” uniform and ribbons with the “B” version, which may be worn while on liberty. Prescriptions for wear of the Blue-White Dress Uniform, which comes in only two variants, are identical to the Blue Dress Uniform, with only the “B” version authorized for wear on liberty.