Red and Blue Team
Based on the main goal of the Red Teaming, the Blue Team should detect any attempts to hack the system and stop the attack.
If the Red Team penetration testing aims to evaluate detection and response capabilities by attacking, blue team security patches any uncovered vulnerability as soon as possible. True and entire purpose of the Red Team is to raise the effectiveness of the Blue Team.
The red and blue team implementation also means regular experience and knowledge sharing for continuous improvement.
More blue team security details.