I might be missing something here, but if you want to know someones gender can you not just ask them?
I'm in agreement with ice pie on this one. I have no problem revealing any info to people personally, you can't lie if you are going to meet someone anyway, but I don't feel anyone should reveal anything they don't feel comfortable with being displayed in a general forum. Any issues with ease of writing lists are easily overcome.
I'm not talking about anything other than sexual preference/gender - why would anyone want to hide that?
Colour etc is irrelevant