well, about the color issue >.>
dragoons servered their king and was always on the front lines, they were noble and only a few were worthy enough to hold the title of Dragoon, *ehrm* anyways Purple is the color of Royalty and since dragoons were i guess high in the kingdom foodchain or w/e lol they adopted the color of royalty from their king
..or something like that, anyways that ~should~ shed some light on a possibility why they choose purple as the color of drgs AF