The patch preview included a paragraph stating that the Dark Green and Magenta colours are to be removed in 17.0 for readability reasons. I assume this is due to their similarities to Green and Pink/Purple respectively, but I cannot say for sure as I have the privilege of not experiencing these issues myself, although I am sympathetic to those who do.
But is it not possible to remove these colours from matchmaking only whilst keeping them as options in custom games and skirmishes? That way people who have trouble with the readability can avoid running into the issue or being forced to use team colours against their will, and at the same time people who don’t have any issues with these colours can continue to use them in more casual environments.
Personally I often lean towards green colours in gaming, and in AOE2 for example I always pick green if its available, but the default Green in AOE4 just feels way too bright lime/neon green which looks out of place to me (I know the middle ages were colourful, but not in that way), so I was overjoyed to see Dark Green added to the game and it instantly became my favourite colour which I pick every game (except when I play as Byz who are purple by imperial decree), so it would be devastating if this update that I’ve been so excited for were to take that away from me when I truly believe there are other solutions to the reported issue.
Please do remove these colours from public matchmaking to preserve readability and accesibility where its most important, but keep them in custom game modes where players have enough control to determine for themselves how much readability they need.