What back pages? The pages are white or cream throughout, but why do you wish to know?
Myself and my friend combined know everything there is to know, but he's not here.
The covers are white card and whatever colour you make them by the images you place on them in the Cover Wizards.
He knows that,
He should have started off saying the covers in his OP then.
(What's the hex color code for the cream color used in Premium paper back pages?)
ESP does not work on line.
and he's asking for a hex code (the RGB code for colour) for the colour of the cream-coloured interior paper.
Indeed, I get that now, due to his further posts. (Why is there no eye rolling emote?)
The Cover Wizard shows hex codes, so perhaps one answer is to create cream-paged blank book, order a proof, scan a page, load it to the Wizard as an image, use the eyedropper on it and see what it says, unless one has some paint software that tells you.
A bit hit and miss though.
Page Glenn and ask him to ask Lulu's print manager if he knows what it is. When the hols have finished that is.