Astronomers use different colors to represent different intensities of
light; the brightest areas of the comet will be in one color and the
fainter areas in another. After all of the colors are used up, the
cycle repeats. So some fainter areas in the comet can have the same
"color" as the brighest areas.
The colors themselves, and the sequence in which they occur, is completely
arbitrary and has nothing to do with how your eye would see the comet
if you were close to the comet.