Have you considered perhaps a nice, rich, candied black cherry? I personally love this colour and think it would lend itself well to the CS-1, with all her gentle curves. The cool thing is that depending on where you shop for your paint, it comes in several different hues/shades/brightness levels, from burgundy to almost black:
Apparently Harley's black cherry is supposed to be quite good, too. It looks black but morphs to deep, dark red in the right light:
It looks to be fairly close to your favourite choice (dark champagne), at least in the same colour palette, and you could even take a queue from the green cafe racer with the sweet paint you mentioned earlier, and put a solid black stripe(s) down the center and fanning off the end of the cowl, following the contours of the bike. Would make a very subtle contrast. I think it would look pretty bitchin'myself but that's just my suggestion. Good luck with whatever path you decide to take. Be sure to keep us posted. It's looking pretty sweet so far.