Although undergraduate (UG) computer science (CS) programs are increasingly engaged in diversification efforts, this work is rarely critically informed or assessed. We conducted a qualitative secondary analysis of interviews with 55 campus leaders at four U.S. institutions of higher education, to examine how diversity initiatives broadened the participation of undergraduate Students of Color (SoC) in CS majors. We found that racial equity work happened predominantly in three types of "counterspaces" - professional conferences, campus identity centers, and student organizations - that explicitly centered and affirmed students' racialized identities, provided community, expanded students' professional and academic networks, and supported students to navigate the racial exclusion prevalent in their classes, the department, and in industry. However, our framework of "diversity ideology" exposed how counterspaces and their leaders of Color operated with little to no support from computing departments, were peripherally positioned outside of broader diversity efforts, and were ultimately inhibited from transforming the dominant culture in CS that privileged whiteness. We argue that studying and amplifying the intentional, impactful labor performed by counterspaces is necessary to address persistent racial disparities in computing.