If you can install floods, I'd do that before going IR. A good BW camera will work well with artificial lighting. With enough lighting, color will work too, though it is always less sensitive and you'll get image graininess at night. Same with day/night cameras - most actually use color CCDs and a straight BW will give a sharper image after dark. If you can pick your lenses and have the subject big enough in the image, graininess shouldn't hurt your ability to identify the subject.
IR is good - we use IR floods in some applications - but you'll get a slightly out-of-focus image under IR unless you focus under those conditions (I haven't experimented with day/night lenses, though). All in all, I'd take artificial lighting before IR, and then it's your choice on whether you'll accept a little graininess after dark to get color during the day whether you go color/day-night or BW.
Bryan