If you properly rotate your shoes, then you may (and should) come upon a day when you have more than one pair of the same style of shoe. When I was in college, I had 4 pairs of Asics 2050s that I was running in, plus two pairs that I had “retired” and used for walking around in. The problem with having two shoes that look alike are that you can easily mix and match a left and right shoe from two seperate pairs. This is a bad thing. Mixing and matching can lead to injury, since your shoes will be at different cycles of their life and can create an imbalance in your stride. A pair of shoes with 50 miles will treat your feet much differently than a pair of shoes with 500 miles in them. If you always put your shoes on a rack in pairs this may not be a big deal, but if you ever need to throw two pairs into the same travel or gym bag for some reason it can be very easy to confuse them.
The answer to this problem is to always label your shoes. How you label them is not important, as long as you have a system that works for you. In my opinion, a way to quickly identify your shoes without spending a lot of time at it is beneficial. You will just want to grab a pair and go when you are ready to start a run, and you will not want to spend the time looking inside at the labels under the tongues.
The way that I label my shoes is to write a letter on the back side of the shoes above the heel in permanent marker. I give each of my shoes a letter. When I used to keep a paper training log, I would start with “A” for each style and work my way up. So, I would have 2050-A, 2050-B, 2050-C, 2090-A, 2090-B, 2100-A, et cetera. Only the letter would go on the shoe itself; the log kept track of what the style was. Now that I am using a spreadsheet on my computer as a training log, though, I have started going up through the alphabet and preceding the style name. So now I have F-2100, E-DSX, I-DSX, G-Zoom, and so forth. This lets me just type the first letter and it automatically fills in the appropriate shoe for me.
I also label the underside of the insole with the letter that applies to the shoe. I normally leave the insole sticking out of the shoe while they dry, but sometimes they get seperated and it makes it easy for me to match the correct insole with the correct shoe.
My system is not necessarily the best system. The important thing is to have a system, and to use it.