Color codes are symbolic systems that align distinct colors with changeable identities or values.

Oxford English Dictionary. Code. 3a. A system of military or naval signals.

3c. Computing. Any system of symbols and rules for expressing information or instructions in a form usable by a computer or other machine for processing or transmitting information.

Examples:

Class by "collar": Working Class as Blue Collar; Professionals or executives as White Collar workers; secretarial class as Pink Collar; Technicians as Gray Collar

Stoplights: Green for Go; Yellow for Caution; Red for Stop

Politics: Red States as conservative Republican and Blue States as liberal Democrat

Race / ethnicity: Skin color as persistent indicator of class, immigrant, or minority status

Question: Are such associations natural and automatic or cultural and learned?

Color code as skin color + other associated issues.

Literary and cultural studies usually represent the extremely sensitive subject of skin color infrequently, indirectly, or symbolically.

Western civilization transfers symbolic values associated with “light and dark”—e. g., good & evil, rational / irrational—to people of light or dark complexions, with implications for power, validity, sexuality, etc., as in the Gothic or Manichaeism.

Literature describes minorities mostly as a historical phenomenon, but physical or visual aspects of human identity may be more immediate or sensory than history. People may interact more easily with others who look like themselves or their family or neighborhood. (Inter-racial marriage is most common among military veterans and people from mixed neighborhoods.)

Skin color signifies as a marker of identity and difference in race, class, or even gender—how much may vary with circumstances.

Dark & light or black & white have many shades between, but terms or descriptions are sensitive and change rapidly to avoid stereotyping. For example,

mulattoes, creoles, half-breeds, mixed-bloods, mestizos, biracial (see tragic mulatto)

in-between color traditionally symbolizes hopes and fears from both sides of a cultural divide.

an in-between person may find him- or herself caught between two worlds, or more or less at home in two worlds.
 

Another in-between variation is the shift of the United States from a "White & Black nation" defined by European-Americans and African Americans (+ Red for American Indians) to a "Brown nation" defined by growing Hispanic populations and intermarriage (mestizo), with white and black minorities.

Association of dark & light color codes with skin color is dramatic but potentially reductive and subject to reversal.

African Americans may find positive associations with darkness not only through skin color but also through associations with night, when slaves or servants found free time for themselves and family, or with images of fertility as darkness, as in Countee Cullen's poem "From the Dark Tower."