I believe in this case you are wrong. Blues and yellow toning is very common on nickel. This seller has many questionable coins, but IMHO, this is not one of them...Mike
My noobish 2cents and all but these are the rules I follow when looking at toned pieces. http://rg.ancients.info/guide/toning.html the following are AT tip-offs: Circular toning spots resulting from the beading of the toning liquid that was used. Colors that blend together out of sequence. With naturally toned coins, the progression is yellow then magenta (pinkish red) then cyan (blue-green). Toning that appears only on the tops of the lettering and devices and not in the coin's recesses. Wild "circus" colors -- on 90 percent silver coins, for instance, army green, bright pumpkin orange, and robin-egg blue. According to PCGS's book Coin Grading and Counterfeit Detection, the following are other indications of artificial toning: The toning floats on the surface of the coin rather than having depth and being bonded to the metal. The toning occurs over hairlines or other marks. The toning exhibits bright "crayon" colors. The toning has a yellow-brown, smoky appearance, indicating it was caused by cigarette or cigar smoke.