Flaking paint revealed the original finish coat for exterior shingles–it looks to be a green stain.

I took advantage of some unseasonably warm (and dry) weather to touch up some exterior paint. As part of my prep, I scraped patches of loose paint, revealing what looks to be the original finish–a green stain. So it looks like the clapboard was painted green and the shingles stained. Not an unusual approach for the period.