The stamp on the right appears to have been printed on some kind of toned or coloured paper:
I think the overall effect is extremely attractive, but I can't see a listing for it in Gibbons Commonwealth catalogue. Gibbons does have a note that reads: 'Stamps on pink paper are from a consignment recovered from the sea and which were affected by the salt water.'
Although to my eyes my copy is more yellowish than pink (admittedly my scan seems to make it look rather pink), I suppose this is the type of stamp they are talking about. If not, I'd be interested in knowing whether Unitrade or any of the specialist catalogues list a variety on coloured paper.
Here it is again:
Ah, they don't make 'em iike that anymore!