Red teaming is the act of systematically and rigorously (but ethically) identifying an attack path that breaches the organization's security defense through real-world attack techniques.
Blue teams are defensive security professionals responsible for maintaining internal network defenses against all cyber attacks and threats. Red teams simulate attacks against blue teams to test the effectiveness of the network's security.
Purple teaming is a security methodology in which red and blue teams work closely together to maximise cyber capabilities through continuous feedback and knowledge transfer.