hmm. A common cause for photos to look orange is the colour balance (for example, setting colour balance to 'sunlight' and taking photos indoors.) Maybe that's what's happening. Or, it could be your monitor calibration...
Take a screenshot with a bunch of photos on your mac, post it here. If it looks fine to us, I'd say it's your calibration (don't really know how this can go haywire, but you never know...) If it's the same for us, it could either be the colour balance you shoot your photos on, or perhaps even the colour profile of the photos. It seems strange that it would do that though.
Anyway, try getting a pic up here so we could narrow down the causes for you
