There is one code that I have been fascinated by for years, the hanky code. This is also called "flagging." With this code, there are different color hankies that a man will stick in his back pocket, and each color means something different, and the meaning changes based on which side the flag is worn in.
I would love to create an updated version of this code for straight D/s or M/s couples. Instead of flagging, maybe a hanky or bandana around the wrist. I already "flag" but in my own way, with my head coverings. Just like with gay males flagging, more than one color could be appropriate at any given time, but one would "flag" what was most appropriate for that day or time. (I am using the term flag in quotes for the straight version since there is no name for the system yet and I want to differentiate between my version and the real, time honored version). I tend to "flag" for whatever head space I am finding myself in more, slave, little, kitten, etc...
In my version, since most people are right handed, anything signifying Dominant or Top is on the left wrist so it does not hinder a Top's "working hand" and anything signifying submissive or bottom is on the right wrist, so their Top is involved in every action of the bottom. These codes are still being thought of, and I have some basics here.
BLACK: High Protocol Named Master/named slave
RED: Heavy Masochist/blood slut sadist
BROWN: Rigger/rope bunny
DARK GRAY: Owner/pet
DARK GREEN: Daddy/little
LIGHT BLUE: Master who owns a slave/owned slave
WHITE: Single Top/ single bottom
PURPLE: Medium Masochist/ pain slut
AQUA: Poly and looking
NAVY: Poly and not looking
ORANGE: Low Protocol Top/ low protocol bottom
LIGHT GRAY: Single Owner/ single pet
LIGHT GREEN: Single Daddy/ single little
YELLOW: Service Top/ service bottom
PINK: Performance or Demo Top/ performance or demo bottom
GOLD: Family Tradition Top/ family tradition bottom
WHITE WITH BLACK DOTS: Domestic Discipline Top/ domestic discipline bottom
MAROON: Domestic Service Top/ domestic servant bottom
ROYAL BLUE: Kitchen service
BLACK WITH WHITE DOTS: High Protocol Trainer
BLACK AND WHITE STRIPES: Short Term Top/ short term bottom (weekend hookup)
NAVY WITH WHITE DOTS: Community Mediator
BROWN WITH WHITE DOTS OR STRIPES: Dungeon Master/ dungeon housekeeper
WHITE WITH RED CROSSES: Medical Personnel
There are more, but these are some of the basics. Enjoy!