According to Thomas Erikson, the Blue, or “Compliant,” personality type excels at logical analysis, research, and fact checking. This type is not emotionally expressive, and is very socially reserved. The Blue personality is very cautious and will work slowly to avoid making mistakes. Blues are often very organized people and live according to set schedules and structures.

Introverts are people who are more socially reserved and need to spend time alone to recharge. Erikson uses the term "introvert” to describe the Green and Blue personality types, who he feels are less social than the Yellow and Red types. The author claims that introverts are “active in their inner world” and have emotions which tend to “operate beneath the surface” (Locations 711, 1743).

Extroverts are people who are socially outgoing and enjoy spending a lot of time with other people. They do not need to have as much alone time as introverts, and are generally more comfortable being the center of attention. Erikson uses this term to describe the Red and Yellow types, who are confident presenters and conversationalists.