Have you checked if the platform is stripping metadata during upload? I've seen sites that automatically convert everything to sRGB and discard ICC profiles, which can cause those greenish blues. On my old laptop, images from certain art sites looked washed out because the browser wasn't color-managed. Maybe test with a simple sRGB conversion before uploading and see if that stabilizes things. It's a pain, but sometimes you have to cater to the lowest common denominator in color space.