I think it's because the image was exported with a color profile. Back in the past, there weren't very many web browsers that supported embedded profiles, but now it's more widely-supported. Unfortunately there isn't really an elegant way to fix it without the original source PSD file - I could take the JPG and color-correct it, but re-exporting a JPG as a JPG isn't really a good practice. I'm not sure that the original artist will still have the PSD lying around.
|