Mexican-American high school students face racial and ethnic identity conflict. Mexico and the US, with different colonial histories and racial systems, reflect different concepts of race and ethnicity. The purpose of this study was to model why and how social identity conflict occurs for Mexican-Americans in light of those differences. In this study, ten Mexican-American Chicago Public high school students, who took Ancestry DNA tests in their high school Spanish class, were interviewed. Lighter- and darker-complected Mexican-American high school students shared their perceptions of and experience with race and ethnicity within the social context of the United States and Mexico. Lighter-complected students were more likely to face racial identity conflict inside and outside of their own community, whereas darker-complected Mexican Americans only faced minor ethnic identity conflict inside their community, but not racial identity conflict. Mexican Americans can struggle defining Mexican within the US system of race and ethnicity, often conflating the two, and creating conflict with traditional Mexican concepts of ethnic identity. Under this model, despite benefiting from white privilege (or "light privilege") in their community and throughout society at large, the lighter-complected students uniquely struggle to adapt to the American concept of race, sometimes being identified as racially white, which in the US conflicts with their Mexican ethnic identity. Their skin tone, or whiteness, becomes an identifier of Americanness. Consequently, lighter-complected Mexican American high school students struggle with identity conflict, and they reflect Goffman's concepts of impression management as they work to protect their identity as "Mexican.". [ABSTRACT FROM AUTHOR]