Ok go for the white bikini as you have a really good tan its simple but a white bikini on a tanned chick just looks hot. As for an outfit to wear I would advise a white mini skirt I don't know if you have ever seen the movie van wilders party but the outfit Tara Reid was wearing was just hot linklink and I'm not even a Tara Reid fan. As for getting cold probably just put up with it for a little while as later you can go in a hot tub or if it gets to cold just flirt with a guy and get his jacket.
If you have thick legs, than don't wear a mini skirt or short shorts.
Do you have shorts that go down to the knees, with very thin material?
Those would look good, casual, simple, and sexy. Let your sexy abs show, but hide your legs.
If you prefer to wear something on top instead, then wear a thin materialed long blouse. Its the type that you can see thru. Long sleeved types are cute. Wear that, only, over your kinda wet bikini. and it will make the guy's imagination go crazy.
If you want to look sexy, then wear white.
White is usually for under the sun though.
Since it is a night thing, maybe green would be best. It is a romantic color.
I agree with the guys. The white color is your best bet. As for the cold part, you can wear your bikini underneath some regular tees and skinnies. OR you can wear shorts and tees with an american eagle zip-up. OR you can just go along with the cold and look hot.