In this paper, we examine a co-design workshop in which youth redesigned a learning activity for critical engagement with computing for the Hour of Code, an annual event that offers hour-long introductory computing activities to youth. We conducted co-design workshops during summer 2021 in two cities with 12 youth of Color (ages 11-15 years), in which we employed different reflective, collaborative and making activities to investigate youths' critical perceptions of computing and address the following research questions: (1) What are the perspectives of youth from groups historically marginalized in computing on critical issues in computing? (2) What kinds of projects do youth create in Scratch to address critical issues in computing? and (3) How do youth reflect on the learning activity and make changes to implement it with their peers? In the discussion, we address what we learned about co-designing a critical computing learning activity with youth.