Shoulder cords are typically worn by members of military, military-related, law-enforcement, or emergency-response organizations during special ceremonies or to signify unique accomplishments or status. For U.S. Army personnel, the shoulder cords are in the branch colors of the wearer’s parent organization, such as dark blue and white for members of the Judge Advocate General’s Corps.
The only shoulder cords Army uniform regulations specifically authorize are for Infantry personnel or for members of special marksmanship teams. But neither do they prohibit the wear of branch-colored shoulder cords, and it’s accepted that local Commanders have the authority to require the wearing of shoulder cords for special occasions or ceremonies just as they may require their personnel to carry or wear branch-colored scarves. However, just as with the scarves, Soldiers are not responsible for procuring shoulder cords; that responsibility falls upon the Commander.
Blue and white shoulder cords are also not specifically mentioned in the regulations of military-related organizations such as Junior ROTC, Civil Air Patrol, or the U.S. Naval Sea Cadet / Navy League Cadet Corps, but this should not be interpreted to mean it’s not a valid color combination for their members. Regulations give broad authority to commanders to assign colors for shoulder cords provided they submit their recommendations to national headquarters for approval.