Maria,
The following information is pulled from the website FAQ link at the bottom of this page. I hope this helps solve your question.
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You should use one of the following color spaces:
sRGB
Adobe RGB
We do not support CMYK or ProPhoto.
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.