Glad you found an answer to your chroma crisis! (Sorry about the alliteration. Too much Stan Lee will rot your brain.) And thanks Tom for working on this.

I've only noticed it with png files. Changing the png metadata color type to 6 produces the colors shown in the screenshot. Color type 6 includes an alpha channel along with the rgb data. As far as png files go, it must be caused by the alpha channel as color type 2, rgb without the alpha, displays correctly. At least that's what I've concluded after some brief testing of changing png metadata settings.