If theses are women, why do they appear to have small shields and lances?

The Mexican soldiers are interesting! They appear to be wearing striped serapes over their uniforms - which seem to be red coats and blue trousers with a yellow seam stripe. This is not a Mexican uniform I recognize except for a much earlier period (1830s-40s)? The headgear seems to be a short shako or kepi with a front plume in 'unusual' colours?

One of the most interesting views of Fort Marion in St. Augustine done while imprisoned.

After 1864 Maximillian's contra Guerilleros led by French Colonel Charles Dupin were wearing red jackets and red sashes. Dupin commanded his Mexican troops untill sometime in1867. I don't know if he only fought Juaristas or also had skirmishes with Kiowa. Since Dupin mostly operated in northern Mexico, it is not impossible. The Uniform as it has been discribed is not necessarily a complete match to what we see on the drawing but may be worth concideration / looking into.

This depiction of the fort stands apart from other depictions in the broader collection which are usually from a birds-eye view right above the fort