I'm using Twenty Fourteen on my newly redone site at davidfeng.com/en, and whilst experimenting with featured pics I found the ones I *just* uploaded after upgrading to Twenty Fourteen (I was previously using Twenty Eleven) turned out fainter.
For example, as I'm an Asian, the colour of my face is what I call "shiny-tan" in iPhoto, but once I upload the pictures via the Featured Image / media upload screen, it turns out pale-tan. I've also tried uploading pictures of cinnamon seats and red belts; they all turn out paler (i.e. with darker tones) now than they used to in iPhoto.
If there was a way I could actually upload a pic showing you the differences it'd might be best. For the moment I think it might be a Twenty Fourteen problem although I'm not 100% on that…
Any help appreciated!