My two children in diapers wear almost the same size and some diapers come without numbers, design changes or any other way to indicate size. Since my kids are only one size apart, it isn't even that easy to hold up the diapers and compare sizes. One could, I suppose, use cloth diapers, but I don't want to.
Some companies understand this. Costco's Kirkland diapers have a different animal on each size. Luvs print a teeny tiny sizing number on them (so as long as you aren't blind you can tell the difference), but the scenting in Luvs makes them unacceptable for children with eczema. It has been so long since I bought Huggies and Pampers mark their diapers, I think, but it has been a long time since I bought any.
But the two store brands that I buy most often -- Kroger and Target have not figured this out. I opened new boxes of diapers for my children the other day and they are covered in adorable blue and green polka dots. Identical polka dots. Baffling polka dots. I took a Sharpie and wrote initials on the bigger kid's diapers, so I could tell the difference. How hard would it have been though to make numbers on the diapers? It could be the store's way of testing everyone for color blindness -- "If you can't read this number, you need to get your eyes checked!" Or something.
It's not a matter of large importance in the world, but I deal with the little things all day long. They get to me. I may not be ready to promise the world change they can believe in so that I can win a Nobel prize, but I do change a lot of bums, and a logical marking system for diaper sizing on all brands and styles would help me out a lot.