U.S. Army regulations authorize only two specific types of shoulder cords—Infantry blue for personnel in that branch, and a blue cord with red and white serrations for wear by all personnel assigned to the U.S. Army marksmanship unit, marksmanship training units subordinate to it, or the Army National Guard marksmanship training unit.
However, it is understood that local Commanders have the authority to prescribe the wear of optional items such as shoulder cords and scarves manufactured in a branch color, typically as part of a special event or ceremony. In such cases, the optional items are provided to Soldiers at no cost to themselves.
Scarlet red is the official branch color of the Artillery Corps and the Corps of Engineers, and as such scarlet shoulder cords could be prescribed for members of those branches. It is also the color assigned to faculty at the United States Military Academy at West Point, including permanent professors, civilian instructors, and registrar.
Other military-related organizations authorize the wear of red shoulder cords; examples include Army JROTC (members engaged in drill activities), Naval Sea / Navy League Cadet Corps (Master-At-Arms and Recruit Division/Company Commanders), and Civil Air Patrol (primary members of a wing’s Cadet Advisory Council).