Judy's own version of "Someday Soon" is - I THINK!! - on her album Who Knows Where The Time Goes, the cover to which is indeed blue-toned and beautiful, and this may be the one you're thinking of. Amazon.com has a bunch of CD re-releases of her old albums and some compilations, and they list what tracks are on which records, and have audio clips; so you may find that some of those old memories are not so irretrievable after all! Worth a surf (but watch out: hate to tell you how much money I've spent on Judy and early Joni recently).
Welcome to Mudcat - there are a lot of us 60s folkies out here! All the best,
Bonnie