IMO Please don't do purple HID's it may go great with your theme but the light output suffers tremendously when getting into the darker color HID's. Don't you want to be able to see at night?
ya you could do a purple headlight housing..but dont do the headlights that color (purple) they are a pain in the *** for the oncoming driver, and they dont give that much light output for you... But i think it will look really good!! Let us see pics after doing some of it and all of it.. we are all "pic happy" haha
I would say go for it if you could get close to the color of the car with it. I think if its a brighter purple like what your engine cover looks like it may look a little funny. But that's just my opinion. Not like its really hard to do or anything so you could repaint it if you don't like it.