@stebsis: I had the same thought as you at first. But after I saw the coloured picture of the young quints, I think the cover this time uses their actual, original hair colour now.
Which means the individual, very different hair colours are just for differentiation purpose. (Assuming no one dyes their hair)
Still, the colours on hardcover(p1) and from digital(p2) does seem to have discrepancy..
Edit:
@ThunderCloud: There's an error in the page numbers in the table of contents. Thought you might want to know. Thanks for the upload.