The Mexican Revolution & Yaqui Indians!
Brace yourself as I prepare to ramble, and having done very little research beforehand the following may be described as more enthusiastic than accurate.
1.) Without being able to put my hands on a copy of the Osprey book, I seem to remember that traditional, ethnic Indian garb in Mexico was much along the lines of 'loincloth and hair parted down the middle.' I seem to remember that some of the Wargames Foundry Wild West Apaches might meet that description.
2.) I seem to remember reading, somewhere, that most Indians employed by the warring factions in La Gran Revolucion served in the capacity as scouts, etc. With one notable exception. That, of course, being the Yaqui Indians who served in conventional infantry battalions. Their dress code was something along the lines of; khaki trousers, khaki jacket, mauser rifle, and severely beat up 'Smokey the bear hat.'
3.) The Yaquis had a rather communal sort of social structure, and pretty dense populations along the west coast of Mexico. The Diaz regime saw them as a threat to central authority and went to great pains in order to destroy the social structure. During the 1880's most of the male population was deported and sold into slavery in Yucatan peninsula, on the east coast of Mexico. The slaves were forbidden to marry women other than Chinese immigrants, in the hopes of eradicating the population of purebred Yaquis. The organization most responsible for implementing oppression of the Yaquis was the Rurales, or the Federal Mounted Police.
4.) And finally, the only instance of which I am aware during the Mexican Revolution in which Yaquis fought in native garb was at the Battle of Nogales in 1913. Rebel general Obregon completely out maneuvered the Federal troops in the State of Sonora, bringing several thousand men up against a substantially smaller force of Federales and Rurales defending the city in an extensive system of trenches. We don't know how many of Obregon's troops were actually Yaquis, but he led the Federale commander, Emilio Kosterlitzky who had been a high ranking Rurale before the revolution, to believe that up to half the rebel troops were composed of enraged Yaquis. Word got out, probably as intended, to the Rurales in the garrison that the rebel army was full of Yaquis bent of revenge against their Rurale oppressors. At one point during negotiations a company of Yaquis were ordered to strip down to loin clothes and begin tribal dancing. This was done just outside Federale rifle range. Obregon's negotiators used the music and what they described as a 'ritual war dance' to further undermine the morale of the city's defenders. The surrender negotiations fell through, but the dancing by scary Indians appears to have had the desired affect. Federale opposition, especially amongst the Rurales, was far less energetic than expected. After a while the defenders sort of drifted across the border into the USA where they were interned for several years in the San Diego area.
Did any of that that actually help?