but we're not talking a bad four colour job here, the re-colour's visual appearance isn't noticeably 'better' than the original besides a new choice of pallette. Comparing the two images, there seems to be equal variations between light and dark and tonal change on surfaces (looking at the jacket, the original has a bit more sharpness to it, while the re-color looks like its a bit softer in how the color varies, which to me isn't enough of a change to warrant a recolour on its own (and I personally prefer sharper differentiation in coloring anyway rather than soft digital brushes).
But I might change my mind when I see what they do with some of the more garish pages in the comic (which I'm skeptical about changing... I mean, its a comic about going MAD in a crazy circus... do the colors NEED to be toned down?)
Timstuff, comparing the recoloured Joker's 5-way Revenge story is a good example: I know the purists will hate me for it, but the re-colour is miles better than the original, which as you said, was limited by the printing technology at the time. But a comic like the Killing Joke which was already exceptionally coloured in terms of technique and technology will be an interesting one to judge.