Extrovert: yellow 24%, gold 24%, orange 19%, red 14%, …
Heller (1989)

Reward Dependence reflects a heritable bias in the maintenance of behaviour in response to cues of social reward. It is observed as sentimentality, social sensitivity, attachment, and dependence on approval by others. Reward Dependence corresponds with Eysenck’s introversion-extraversion trait.
Low Reward Dependence: independent, non-conformist, practical, tough-minded, cynical, unwilling to share their intimate feelings with others, socially detached, irresolute, insensitive to social cues and pressures, content to be alone, minimally motivated to please others, act for immediate gratification, social withdrawal, with aggressive anti-social behaviour detachment, coldness in social attitudes. Individuals low in Reward Dependence are practical, tough-minded, cold, socially insensitive, irresolute, and indifferent if alone.
High Reward Dependence: sentimentality, Openness to warm communication or social sensitivity, Attachment, Dependence on approval by others, greater need for social rewards and verbal approval, ambitious, warm, warm social relations, sentimental, pleasant, sociable effective communication, sensitive, recognize salient social cues, sympathetic, genuine care for others, socially dependent, persistent behaviours, easily influenced by emotional appeals, learning from reward signals, persisting repetition of actions that are associated with rewards, increased sociability and a need for social approval. Individuals high in Reward Dependence are tender-hearted, sensitive, socially dependent, and sociable.
(Cloninger, 1994)

You can see seven traits that correlate with each other, i.e. people who are sociable, impulsive, active, risk-taking and expressive, and lacking consideration and responsibility. This combination of character traits produces a new and more general character that is called extraversion.
(Eysenck & Wilson, 1977)