Are color themes strictly limited to 5 colors?

I can see that 5 is a nice limited number and usually am happy to stick with that limitation, but I often want to add just 1 or 2 additional colors from a photo, say, and I can't figure out any way to do this.  If not, is there a recommended method for recording a slightly longer list of colors for reference? Another app? I've been sampling and painting color patches into a photoshop page as a workaround, but I'd think that capture would be perfectly suited to handle this.