Within reason, obviously. What I'm saying is a NOS frame is not going to go for significantly more than a 'used' one in the same way it might for something rare/boutique. You might have some luck on eBay, but honestly, I don't see anyone here being that fussed. Might be worth sticking it in the Cannondale thread though just to see. Your market is a very specific person - someone who wants one of these frames and wants to pay the premium for NOS of the less popular colourway. A silver/black one in 56 is about £300 - that's what I paid for mine and that's what I'd sell it for. Even then, it might be tricky.
I'm not trying to be a dick, just trying to give some realistic advice. You'd deffo be better splitting it if you want to sell as NOS.