Hubble Images of Pluto: Image credit M. Buie /NASA, ESA, Southwest Research Institute
Often you see illustrations of Pluto as being white, but really, it's red. This is just one more link showing the Pluto is a big Kuiper Belt object (these are red too, due to UV action on the organic compounds in their ices). The black parts in the image probably represent organics that have been polymerized into taryy gunk.
Back in 1994 Hubble took some images of Pluto and made a map of the distribution of reddish patches. Not bad since Pluto is pretty small even in Hubble, and a lot of features are only a couple of pixels wide. Now Hubble has released a new map,which shows changes since 1994, the north pole gets brighter and the south pole darker over 10 years. There are some more images here, and a great animation of Pluto rotating here. Sure, it's interpolated to heck and back, but it sure is fun.