This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to choose a goalie pinnie
Choose a colour other than your team's.
You may think this step is crazy, but it's true. If you're wearing a blue goalie pinnie, and your team's colour is blue, you won't be allowed to wear that pinnie in play.

Available options: --Ultimately, the fashion choice is up to you! Keep in mind the season. Right when you're having a match, or make a bid for a tee, you'll have the opportunity to notice the players' clothes.; --This is because the referee can't easily tell who can pick up the ball, and neither can the other team. This gives you an unfair advantage, which is why it is illegal.; --If team a allows you to wear it, go for it. Choose a color other than team b's color scheme.; --If you do, go with this refrain : Consider the color that you're going with. You can go pink or black, you can go girly, etc.;
The answer is:
This is because the referee can't easily tell who can pick up the ball, and neither can the other team. This gives you an unfair advantage, which is why it is illegal.