People critical to this would certainly claim that it’s difficult to categorize people, but, of course, this method includes numerous variations, and most people have more than one color. Another critical comment might be that dividing people into groups is something that should be prevented, but Thomas Erikson doesn't value one quality more than another, he just states that we are all different. This is just a way to understand each other. We get to know the cause of conflicts and how best to treat them. Of course, this is not a totally waterproof method. People are unpredictable and complicated. The reality is always more complex.
The book, a new edition, is entertaining and useful, both at work and in private life. Everyone benefits from this because everyone we all use communication.