Until now, all photos of the comet 67P/Churyumov-Gerasimenko have been in greyscale. According to a research paper that will be presented at the American Geophysical Union's 2014 Fall Meeting, you are looking at its first true colour photo, taken with Rosetta's OSIRIS camera.
The reason why the image is blurred is because the comet moved between exposures, as a Reddit user showed by separating the RGB (Red, Green, and Blue) channels in the composite colour image and making this animated GIF:
Here's the same photo sharpened and colour corrected, made by another Redditor:
For reference, this is a colour photo of Mars taken by Rosetta's OSIRIS camera using the same multiple exposure technique: