Halls of Montezuma: A Battle History of the U.S. Marine Corps - Wikipedia

And a better explanation and summary is here.
https://www.mcrc.marines.mil/News/News-Article-Display/Article/519657/historic-battle-of-chapultepec-remembered/

The information given in the USMC Recruiting Command article about Marine officers and NCOs adopting scarlet "blood stripes" after the Battle of Chapultepec is a myth of the Corps that is difficult to overcome. The history of Marine Corps uniforms is amazing enough without adding myths to it. Trouser stripes were a popular part of both European and American military fashion since the Napoleonic Wars, and at the time of the battle in 1847, Marine officers wore a blue stripe edged red on their dress trousers. Enlisted men wore no trouser stripes. That did not change until 1859 (if not earlier), when trouser stripes for officers went away, and they wore a red welt in their trouser seams in both dress and undress. Except for the most senior SNCOs, enlisted men wore no red welts on their trousers, and this condition persisted until 1892, when red trouser stripes were authorized on dress and undress blue trousers for officers and NCOs in the rank of sergeant and above. Corporals were authorized to wear red trouser stripes on their blue trousers beginning in 1896. Non-rated Marines (Pvt then; today the grades of Pvt - LCpl) were not authorized trouser stripes. The width of the trouser stripes was regulated by rank, as it is today. Throughout the 19th c., Marines wore white linen dress trousers during warm-weather months, and these had no trouser stripes or welts.