I just had to weigh in here, with regards to the pink halter and a male horse looking embarrassed.
We've got a little dark bay gelding at our stable and we all like to joke about how he's gay, and a completely stereotypical gay. He wears a pink halter, and he STRUTS in it! You can almost hear him saying "Fabulous!" as he minces.
The easiest way to tell a male from a female? The female horses are the ones who're always talking and nattering to each other and never shut up. The males are the ones that just grunt when you ask them a question.