These icons were made with the precise color code as the team colors. I don't believe they have an issue with their brightness, but it's also probably the easiest icon to modify on this website.
Here's an example of the first 10 colors in-game.
edit: well, to clarify, I kinda yeeted some colors in that screenshot as it was first-generation implementation, so the blue for instance does not match the uploaded blue here. All uploaded here are indeed color matching and were remade