From the FAQ page:
Q: When I upload an image, why are the colors reversed?
A: You need to save your images using one of the following color spaces:
sRGB
Adobe RGB
If your images are saved in CMYK, you may the see the colors get inverted when you upload them to Fine Art America.
Resave your images in sRGB or Adobe RGB, and you'll be all set.
I hope that helps, Don.