CAC green bean simply means that a coin is solid in the grade which the
TPG assigned it. It's really more just a way for a would-be collector to gain a bit of confidence that the PCGS grade of this coin is, in CAC's opinion, accurate, and that this coin is a good quality representative of its assigned grade.
The toning has nothing to do with it; CAC will sticker everything from blast white and brilliant luster gems to heavily toned monsters. Eye appeal is not always the main factor. In this case, CAC is not necessarily claiming that this is an exceptionally beautiful or pretty MS67 FSB Merc, just that they agree that the coin is worthy of being slabbed as MS67 FSB; they leave it up to you to decide if the eye appeal is there or if you'd prefer less or more toning.
I know this seller, and the coins tend to look quite a bit better in hand; I purchased my 1806 50c there and it ended up being quite a bit nicer than the photos.
Member
ANA - EAC - TNA - SSDC - CCT #890
"Most of the things worth doing in the world had been declared impossible before they were done." -- Louis D. Brandeis