This question allows us to peep the variety of perspectives in the world of sexploration.
Some scenesters recognize "purples" as people in the BDSM scene. These folks gather in places like The Purple Palace, wear shirts that say Perverts Wear Purple and join groups like The Purple Rose Society.
To others, "purples" are people in the gay, or LGBTQQ, community. These folks use travel agencies like Purple Roofs, take tours with the Purple Dragon and use directories like Purple Unions.
Some "purples" simply have a purple fetish and shop at, of course, The Purple Store.
"Purples" also refer to members of the Purple Jedi Order:
The Purple Jedi must blend loving discipline with nature's cruel passion; idealism and reality; individualistic search for power and place in the Galaxy balanced with the good of the whole. We are the light in the dark by being aware of our own darkness. We seek to embody BOTH the Jedi Code and the Sith Code. Mutually entwining both the right-hand path and the left-hand path...The most important thing to remember is - there is no wrong way to do it. Whether you are already a "purple" or just "purple curious," do it without apology!