These HST data are from proposal 10774: H.A. Weaver (JHU/APL), S.A. Stern and J.R. Spencer (SwRI), M.W. Buie (Lowell Obs.), E. Young, L.A. Young, and A.J. Steffl (SwRI), M. Mutchler (STScI) and W.J. Merline (SwRI).
This image was originally black and white and recorded only overall brightness. These brightness values were translated into a range of bluish hues. Such color "maps" can be useful in helping to distinguish subtly-varying brightness in an image. The colors in this image are not what human eyes would see looking at Pluto.