Like the other branches of the Armed Forces of the United States, the Marine Corps prescribes the wear of Service necktabs by female personnel with certain uniforms, but the branch stands alone in issuing necktabs in three colors: black, green, and scarlet. Service necktabs are the equivalent of the four-in-hand or long neckties worn by male personnel.
The rules regarding which color necktab female Marines and Officers are to wear are somewhat complex. The green Service necktab, for instance, is always worn with the Maternity Service Uniform when the green tunic top and/or long-sleeve shirt are worn—but the necktab is not worn with it if the short-sleeve shirt is worn without the tunic. (In that case, the short-sleeve shirt is worn with an open collar.)
Rules regarding the wear of scarlet (Marine regs frequently refer to it as “red”) necktabs changed in 2005, when the decision was made to require wear of the scarlet necktab with the female Officer Dress Blue “A”/”B” uniforms. Black necktabs are worn with the Blue Dress “A,” “B,” and “C” or Blue-White Dress “A”/”B” uniforms.
Please refer to the Marine Corps manual regarding exact instructions regarding wear of Service necktabs, and be aware that they are not the type of necktab worn with uniforms prescribed for formal social occasions. Those are known as Dress necktabs and are have a crescent or quarter-moon shape in the front; they are the equivalent of the male’s bow tie.