I work in an advertising agency, and once we were renewing the package design for a local chocolate factory. It's a small chocolate manufacturer, so the owner himself reviewed our suggestions. He liked one of our designs, but noted that the piece of chocolate on the cover was "wrong brown, too red" and that some detail should be changed somehow, don't remember now what it was. We said that it was exactly the same they had used before, but that we'll make the adjustments he wanted.
Next time he came over to see the package the detail was fine to him, but still that brown was "weird, too red somehow". We said that OK, what if we change the color right here on the screen and you say when it's closer to what you think it should be. After a strenous process of searching for the right tone and making printouts to see what different tones of brown look like on paper, the client got frustrated (we were already past that point ages ago) and concluded:
"This is going nowhere. I say it's too red, but you disagree. Maybe it's my color blindness that makes this so difficult."