Wow, this is really very useful information. I have long wanted to know what the colors of the passport stand for. In fact, it is very interesting and quite logical, why countries have chosen such colors. Still, I would add yellow, as I think it is a very bright and memorable color. Recently, my husband and I were faced with the problem of forged documents. A man with a fake passport wanted to check into our hotel. We didn't even distinguish it from the real one, but on intuition I decided to scan it in the https://www.idanalyzer.com/products/prime-id-scanner.html . The program, of course, quickly declassified the stranger, and we had to call the police.