The shoulder rope of aid-de-camps to general officers stems from the practice of both and French and English officers serving in th functions of aides wearing a rope with a pencil tied to the end of it to have it handy for transcribing orders from thier General. That transferred over to the Contitental Army.
The Marines (2/6th and a regiment from the 5th) were awarded the French Fourrage after WWI and contiue to wear it as tradition.
Not sure why the Infantry wears the blue rope. Didn't cover that at Knox or NJROTC. lol
"Growing up as both a Southern and the son of a child of the '50s, I was imprinted with several things that have long stuck with me. The F-86 Saber Jet was the finest fighter ever flown, the National League is always superior, and Leslie Coffelt
was the finest revovler shooter since Mr. Ed."