I have a classic example of not being able to see 
flaws in scans, but up in person you can. I got a 
new AnC cel. You don't see any problems with the 
image and such, the dealer doesn't state any, but 
well, hope they start to state conditions because 
it had damage to it. -_-;; It was delivered in 
steel protection, so it was there and sold to me 
damaged. Plus, line fading I wish I knew too, but 
you can't see any of that in scans sometimes. It 
has to be a huge error or problem for it to show 
I suppose. I dunno, speaking from anything I've 
been through. I wish I would have known before 
buying though. Just wont buy too often unless 
stated from now on. Same old thing I suppose. 
That's why I love certain dealers who tell you 
the condition from their own eyes exactly what 
condition it is in. But, some people are not too 
familar maybe with certain problems, who knows? I 
suppose there is a site for knowing how to tell 
what is a problem and such or what is normal, 
dunno, forgot if anyone mentioned it if there 
was. Dunno, something ya have to talk to with the 
person you bought it with if you are unhappy with 
the condition and were not told about it. Maybe 
they thought the rainbow colors was part of the 
image if they were not familair with the anime? 
Well, long shot, but who knows?

Returns are really not done, especially on Ebay 
or auction, probably not done, most of the time 
they can't be done, but if there is a problem, 
big one, then they should have known as well if 
it's noticable in person. Depends if they knew 
what to look for as well. Just give them the 
benefit of the doubt as well, and well, talk to 
them about it, see whay they say and how they 
react to it.

Anyway, hope you figure out a solution.