Here's an
ebay listing suggesting that color misregistration exists on that US Revolutionary War issue. How common is probably an unknown, but it happens. Values can be all over the place, though. Generally, they may command a premium, but not to the point of being "valuable" as a true error would be. In fact, they would be classified as more of a "freak" than an "error" and since there is no one accepted catalog upon which to base values--it usually depends upon what a buyer is willing to pay and what a seller is willing to accept in order to value the item:
http://cgi.ebay.com/us-stamps-error...ht_813wt_905Interestingly, as with many stamps of that era, they were printed by Photogravure method on the Andreotti Press, which has been known to produce a number of color misregistrations. In fact, here's an example I posted in another thread yesterday that although it is an entirely different stamp, it too shows a color misregistration and was produced by the same Photogravure method on the Andreotti Press:
