I've read in other places the colour blobs can fade with time? I can live with the shadowing along the bottom because it's still infinitely preferable to jiggling some stupid clip-on light around - and I don't notice it anyway - but I just got my second Paperwhite delivered (the first arrived pre-bricked, shall we say, and is on its way back) and it does have a certain small, faint pinkish blob at the very bottom. It doesn't bother me hugely, but for the money I'm paying I want as close to flawless as possible; but if there's a chance it'll fade after a few days, I'll take my chances until then and see if it improves.
I saw on a Kindle forum somewhere that the colour discoloration might be down to some form of residue on the screen, perhaps from the plastic bag wrapped around the device when it arrives. Anyone got any thoughts on that?