|Slight difference in color can make a shirt a favorite or a return (and in the catalog, the shirt on the left looked more like the shirt on the right).|
The shirt on the right "pops." It looks great. It is one of my favorite shirts.
The shirt on the left, with the exception of the navy stripes, is drab. The light blue is more of a silver(y) light teal, and the collar and placket are off-white, not pure white. (It is not yet worn and will be returned). The one on the left would look uninspiring on a man or a woman and the one on the right would be great for either.
These items can look the same in a catalog or on a web page. Even under store lighting the differences can be obscured. (Thus another negative aspect of shopping in malls - it is often a challenge to take a good look at an item in daylight. I am forever getting permission from shopkeepers to take items I am considering purchasing outside, in order to make a more accurate assessment.)
The point is not to judge people for wearing "the wrong shade." People should wear what they like.
Rather, it is to appreciate that these subtle differences at all, just a few hertz, can often make or break an item. It can determine whether a shirt is destined for heavy wear, or the back of the closet. (If you buy well, you don't have to think about what you put on each morning.) For the vendors, getting the color right can mean the difference between happy and repeat customers vs. returned items, and correspondingly the difference between financial success or failure.
See also: Blacklisted Colors