A top-of-the table English Women’s Soccer League game with a crowd of nearly 33,000 has suffered a delayed kickoff in London because the teams had matching socks.
There's probably a rule or something that says the entire kit has to be different. And if you're in a scrum with your head down looking at the ball, you're not looking at the other players jersey colour so different socks is how you tell team mates apart.
To be fair, the referee is officiating a professional sport where you really need to be able to clearly distinguish between the legs of two people lunging quickly for the same ball with their feet.
Probably sounds silly, but when that's what 95% of the sport revolves around, you can understand them being picky on a detail like this.