Dissociative Identity Disorder: A disorder categorized by having distinct headmates and amnesia
Orange was chosen because of its association with Halloween- in media, people with DID are depicted as being "scary," or (in the case of Split) monsters. This is a subtle attempt at reclaiming that stereotype. Purple was chosen as a complement, but also doubles as a Halloween color, which is purely coincidence
A 5 striped flag, with all the stripes vertical. The leftmost and rightmost stripes are orange, with the large center stripe being purple. Between them are thin white stripes (or transparency, for the transparent version)