Help with rugby studs?

Hi i am purchasing a pair of boots in the near future and i need some help. I am very fond of the adidas power swerve boots and i understand that there is a blue pair designed for rugby. However i prefer another colour but these only come in blades and i asked by coach and he said platic blades are ok i just need to know if anyone can certifie that platic blades are legal in rugby as i know metal blades arent?