I know in the past that any photos that were too big a file size would show up in that dull green way, or if I edited the photo's size right here in Weebly, they would lose their nice colour too.
But all my verticals have been showing up correctly for several years now. Weebly must have changed something. I even tried making the verticals the same pixel height as the horizontal photos, but they still turned out the same duller colour with green undertones.
I know it's not my photos, as they post perfectly on Facebook. I don't know what to do about it at this point, and I'm hoping this is just a temporary thing, as it would be a real shame if the vertical photos stayed this way.
Update: I figured out a way to get my photos to come out the correct colour - at least on my monitor - so have been replacing all the vertical photos with larger versions.