yeah go for it man, its your car, im not saying dont, but i gotta admit, it does look good with both low and high beams on HIDs, my bulb failed on me <_< ( damn H4s ) attempting this look :P
up to you on what colour, my mate had purple on his foggies, but as i said, you wont be using high beams much, its still up to you if you want to get it, even if its just for flashing people, note that it still needs to warm up,
nahh not a good idea, i got hid on my high beams, and barely use em, and ofcourse it will blind people, HID for foggies is okay, but go for the temp of 3000k imo