I think I may have posted about this before, but I couldn't find it, so here goes again. I'd at least like to see if anyone else can verify my findings…
It seems that Aperture's choice of color profile for its previews has some rather wide implications. In a RAW workflow, previews are assigned an Adobe RGB profile. In a JPG workflow, previews aren't generated at all at first (which makes sense - no need to create a JPG from a JPG), but they are created once you edit a photo. Then once again, the preview is assigned an Adobe RGB profile, irrespective of the color profile of the original photo. This all kind of makes sense. Presumably, Adobe RGB is the same as, or close to, the color profile Aperure uses internally.
The problem comes when photos are “shared”. With the Aperture preference set to “Share previews with iLife and iWork”, Aperture generates an XML file that can be used by external programs. This XML file points the external program at the previews (or the original in the case of an unedited JPG). Then photos can be picked up in various places:
* In mail.app via the Photo Browser.
* In any app via the Media section in Finder.
* On an Apple TV via the “Choose photos to share” option in iTunes.
BUT - all these photos (with the exception of an unedited JPG) will ALWAYS have an Adobe RGB profile. This is generally not good, since the photos will display badly in any app that isn't color managed. Unfortunately, this seems to apply to Apple TV. Photos there have the typically subdued look of Adobe RGB when not color managed. The situation actually gets worse with JPGs. An unedited JPG which originally had an sRGB profile will display fine, but as soon as you edit that photo in Aperture, it will display badly because now iTunes/Apple TV is working with an Adobe RGB profile. I've done tests and it's painfully obvious. This seems to me to be a rather serious shortcoming with Aperture or Apple TV!