Add this to our earlier postings (here and here) about the World War 1 practice of camouflaging horses by coloring them with paint or dye. Anon, PAINTING HORSES FOR SERVICE in Northern Times (Carnarvon, Western Australia), January 13, 1917, p. 5—
Protective coloration for military equipment—a lesson in the art of warfare taught extensively on the battlefields of Europe—is being put into practice on the Mexican border says a contemporary. Schemes to render military equipment invisible at comparatively short distances as in vogue in Europe today include the dyeing of horse so that they will merge with the landscape, covering the embankments of isolated batteries with foliage, and painting warships with wavy streaks which have the effect of making them hard to distinguish against the background of a heavy sea. Dyeing a horse to remove his distinctive coloration is one of the first of these lessons to be applied by the United States army on the border. The dye which is in use at this time in the cavalry and artillery camps along the Rio Grande, when applied with a grooming brush or sponge after the hair of the cavalry mount or artillery horse has been thoroughly dampened, will change a dark chestnut to a yellow dun. The animal so treated has been found to be almost invisible at any distance over five hundred paces. It is an easy matter, according to army veterinarians, to vary the strength of the dye used so as to approximate almost the exact coloration of any locality.