That is a nice shade of purple!
That's definately from the cold. -1 might do some damage. If you can, make a greenhouse around them by putting up four posts taller then the plants and wraping them in plastic at least at night, I had to do this for some long seasoned heirloum red Habanero peppers. Just make sure there isn't any moisture in there put some dry straw in the bottom around the stem up to the first leaf set. The humidity might get high so keep an eye out for bud rot. :thumbsup: