Thomas Erikson is a Swedish behavioural expert who spent decades studying how people behave in work and relationships. His book is built on a deceptively simple premise: most people's behaviour can be understood through a four-colour framework, and most conflict between people comes from assuming that others think and process the world the same way you do. The four colours map to the DISC model, a well-established framework in organisational psychology. Red corresponds to Dominance: task-focused, direct, decisive, results-oriented. Yellow corresponds to Influence: people-focused, enthusiastic, persuasive, creative. Green corresponds to Stability: people-focused, steady, supportive, reliable. Blue corresponds to Conscientiousness: task-focused, analytical, systematic, detail-oriented. Erikson is careful to note that no colour is better than the others. Each has genuine strengths and characteristic weaknesses. Most people are a blend of two or more colours, with one or two dominant, though the blend is unique to each individual. The value of the model is not categorising people into boxes. It is recognising that what looks like stubbornness in one person is actually a different processing style from your own, and that adapting how you communicate to the other person's style produces dramatically better results than expecting them to adapt to yours.