That's good advice, but I can't because the originals are bigger than Tapas allows. And I don't mean the file size, I mean the length and width are too large. Maybe I've missed something very obvious, but I don't know of a way to shrink a jpg that isn't basically what I've already been doing. 
Again, I don't actually think the file is the problem because when I first posted to Tapas and Webtoon I used the same file, no changes. The colors only appeared altered on Tapas.
