I can't easily get the number of actual pages processed, so rely
on telling the (rather hacky, and surprising - I have to
divide to a separate counter to force an integer result) macro
the number of pages used before the current numbering started.
That way output where the colour isn't appropriate, such as Nook or the newly introduced
A4Lulu output (which is the A4 book but with white cover page and no end coloured page, and so
suitable for using as the content on Lulu, where the cover is separate) can omit the colour.