Mervyn C. Alleyne is a Trinidadian sociolinguist.
Race, then, is the socialized perception of phenotypical characteristics. These phenotypical characteristics constitute only one of the features recognized and used for human classification. Behaviour and customs (language, clothing, foods, religion) constitute another set of features and, together with race, provide the basis for ethnicity.
Racism intersects with ethnocentrism. Racism is the belief that phenotypical or alleged genotypical characteristics are inherently indicative of certain behaviours and abilities, and it leads to invidious distinctions based on a hierarchical order. Ethnocentrism is the belief in the superiority of one’s own culture.
When a people come to believe that their assumed superiority is based on a superior genetic pool, it is a pathological case of racism and ethnocentrism combined.
Western European languages are full of metaphorical expressions showing this semantic development of colour terms. In at least some cases, the affective associations and the metaphorical usage are clear and consistent. Yellow, for example, has a rather consistent association with cowardice and other kinds of pejoration in English (cf. yellow-bellied, yellow streak, the yellow press). According to Ferguson (1954, 268), in the Renaissance, yellow was used to suggest jealousy, treason, deceit. The traitor Judas was frequently painted in a garment of dingy yellow. In the Middle Ages, heretics were obliged to wear yellow. In periods of plague, yellow crosses were used to identify contagious areas.
Alleyne, M. 2005. The Construction and Representation of Race and Ethnicity in the Caribbean and the World. Kingston, Jamaica: University of the West Indies Press. Kindle Edition.