Eau-de-Nil

Death assures a wise old hermit that this is the colour of infinity. And who is to argue with him? He's seen it. (Soul Music)

Probably coincidentally,the colour appears again as the theme of Harry King's daughter's wedding.

Annotation

Some years ago, eminent scientists worked out that what with the red shift and the constant expansion of the Universe and particular conditions applying during the Big Bang, if the Universe has a colour at all, it would be the sort of pale pastel blue-green which we otherwise know as eau-de-nil.... by a funny sort of coincidence, this is the nearest that we can get to approximating the eighth colour of the Discworld spectrum, octarine, which is described as a kind of bluey-purpley-green colour, but not really... It is possible the Universe has a lot of surprises for us to discover.