CG Bob is right, in that the various regulations for painting USCG and USRCS vessels, as posted on the Coast Guard's web page, are about the best guide we've got for such things. I do think, though, that there's a mighty big gap between the Morris class (with launching dates in the 1830s) and those 1894 regulations. I don't have a really solid source for this assertion, but I don't think the practice of painting spars yellow (or "spar color," as the Coast Guard eventually came to call it) appeared prior to the 1880s or thereabouts.
I've only seen half a dozen or so contemporary, color illustrations of mid-nineteenth-century American revenue cutters. All the ones I recall have black hulls, sometimes with white moldings. (Some time back we had an interesting discussion here in the Forum about the possibility that the steam/sail cutter Harriet Lane had a green hull. I asked Bob Browning, the Coast Guard Historian, about that; the idea was news to him, but he didn't have any firm reason to confirm or deny it. That's how things usually work when it comes to the early days of the Coast Guard and its predecessor organizations.)
I can't recall having bumped into any evidence whatever about the painting of the inboard works of revenue cutters. White strikes me as the most likely - but I think a medium, slightly greyish green would also be a possibility. (The Navy was painting inboard works in that color at about that time, though white seems to have been increasingly popular.) The old custom of painting the inboard works red was certainly out of date by that time.
All this serves to emphasize how awful the records of the Coast Guard's predecessor organizations are. It's really a shame that such attractive ships - and good model subjects - are so poorly documented.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.