My work uncovers overlooked experiences of racially ambiguous people in the postemancipation British Caribbean and US. Scholars tend to define these societies as failed experiments in racially inclusive citizenship, but in doing so they rely on dichotomies like black/white, free/enslaved, and success/failure. I place racially ambiguous people in their frameworks. Instead of addressing those whose physical traits defied easy categorization--e.g. people of "mixed race" who "passed"--I analyze subjects whose "black" or "white" appearance came into conflict with typical racialized assumptions of normative behavior. For example, "black" Jamaicans who voted in favor of white landowners in local government were accused of disloyalty framed in terms of ambiguous identities: they were "black" men with "white hearts." I discuss four means by which ambiguity was created: transracial adoption, political participation, economic practices, and sexual habits. Subjects include former slaves adopted by white families, and their understanding of national belonging; black Jamaicans accused of acting white and excluded from an imagined exclusively black community for doing so; depictions of African Americans as "prosthetic" citizens in the postbellum US white "political body"; and white sectarian missionaries in the Caribbean and carpetbaggers (Northern officeholders in the US South); both were accused of racially impure sexual tendencies and relationships to property by white supremacists seeking to reclaim citizenship as exclusively white. I trace common vocabularies and experiences of ambiguity in both locations. In particular, I uncover a transnational conservative movement that opposed racial equality, and shared means and objectives of undermining its proponents. In its focus on racial ambiguity, the study adds to discussions about postemancipation societies, racial identity, black nationalism, and white supremacy, revealing more complex and contradictory pictures in each case.