More Detailed or obscure list

Hanky Codes

You cannot go wrong with the primary colours, it get a little harder when you need a Pantone© Colour match chart to determine where they are into, let alone adjusting for the light level or if they washed it with something else!
There are other lists such as the one at the In Search of Men web site "Codes". There are lots of things which signal what the guy is into - like if you are in full leather you want a leather guy, if you have a paddle hanging from your side it is planned to be used, and so on. This is fine for the clubs and a gay space - but Hetros copy gays boys without understanding any unspoken implications, its just fashion. They are just copying a guy in the street just like any fashion.
This has now transformed into BDSM guys being less subtle about their dress code - especially in  London where you are competing against exotic 'high fashion'. In other countries (previously gay strong holds) there is almost no signalling -  like in Germany they have an expression "you have to open the box to find out what is inside" - this has the advantage that none of your signals can put off the other guy; you take me as you fine me!