At first, intermixing between slave and master was undoubtedly met with shame, humiliation, and rage, since such children were the result of rape. However, since the percentage of men who will knowingly commit incest is lower than the percentage of men who will commit rape of any female, the female products of these rapes may have seen an improvement in their circumstances, when compared to other enslaved females. Therefore, the preference for lighter color begins, as mothers notice that their lighter-skinned children are treated a little more favorably than their darker-skinned children. This is not to suggest that lighter-skinned slaves were not treated in an abominable manner, nor that all lighter-skinned slaves received preferential treatment, but there was certainly enough of a difference to make mother's notice this. In fact, the supposed difference in I.Q. between light-skinned and dark-skinned blacks has been proven to be attributable to differences in environment, rather than genetics, supporting the theory that light-skinned blacks received some degree of preferential treatment.

Furthermore, the difference in social class systems in the United States and the rest of Latin America helps explain how colorism developed differently in these areas. The United States had a much greater percentage of poor white immigrants, who needed to elevate themselves above someone, which helped lead to the concept that even white-looking African-Americans were slaves, if born to slaves. In contrast, most Latin American countries did not have a tremendous influx of poor white immigrants, which meant that there was not the same motive for colorism. Furthermore, because there were not as many formal restrictions against mixed-race relationships, people could see actual improvement in their financial status and life circumstances by examining a lifetime's worth of interracial relationships. Since whites had the power, a preference for "marrying white" would be developed, which, though initially based on power, would become ingrained in the culture. In the United States, though they may have initially been treated more...

However, the high degree of intermingling also made it possible to recognize physical similarities in African-Americans, which helped break down some social barriers. This helps explain why lighter-skinned blacks receive preferential treatment in the workforce. However, the absolute system of color-based discrimination has its vestiges; in the United States, black women very rarely marry white men, perhaps as a nod to the fact that for years they had no option of saying "no" to sexual advances by white men. Moreover, black men have a preference for lighter-skinned black females in the marriage market, perhaps because they recognize that the children of those relationships are likely to receive better treatment from society than darker children would. Clearly, then, colorism is a rational response by an oppressed people to a system of colonialism. The challenge is how do people no longer living under a colonial yoke, divest themselves of hundreds of years of conditioning and adaptation, and rid themselves of colorism? That is a question that I cannot answer.
Works Referenced

Cruz-Janzen, Marta I., "Latinegras." Frontiers, 22.3 (2001): 168-183.

Goldsmith, Arthur, Darrick Hamilton, and William Darity, Jr."Shedding 'Light' on Marriage: the Influence of Skin on Marriage for Black Females."

Goldsmith, Arthur, Darrick Hamilton, and William Darity, Jr. "From Dark to Light: Skin Color and Wages among African-Americans."

Goldsmith, Arthur, Darrick Hamilton, and William Darity, Jr. "Shades of Discrimination: Skin

Tone and Wages."

Hill, Mark. "Skin Color and Intelligence in African-Americans: A Reanalysis of Lynn's Data."

Population and Environment, 24.2 (Nov 2002): 209-214.

Telles, Edward, and Edward Murguia. "Phenotypic Discrimination and Income Differences among Mexican-Americans." Social Science Quarterly, 71. 4 (Dec. 1990): 682-696.