The pictures taken by Rosetta are BW. From [0]: "Some light contrast enhancements have been made to emphasise certain features and to bring out features in the shadowed areas. In reality, the comet is extremely dark -– blacker than coal. The images, taken in black-and-white, are grey-scaled according to the relative brightness of the features observed, which depends on local illumination conditions, surface characteristics and composition of the given area. Some slight vignetting can also be seen in the corners of some images." So possibly Philae has a similar system. [0] https://www.flickr.com/photos/europeanspaceagency/1573996637...