Magic-sized clusters are atomically precise nanoparticles that eliminate heterogeneous broadening, thereby enabling narrow ensemble emission. However, the discrete structural stability that causes only certain sized clusters to exist also inherently disallows continuous optoelectronic tunability. New strategies are required to allow magic-sized clusters to continuously cover regions of the visible spectrum. Herein, we investigate the atomic structures of two oleate-ligated Cd3P2-450 and Cd3As2-525 clusters and conclude that they are structurally homologous based on pair distribution function analysis. The structural similarities between Cd3P2-450 and Cd3As2-525 allow alloying of P and As in these magic-sized clusters without perturbing the structure or the impressive optical properties. Ligand exchange for phosphinate then produces Cd3P2-xAsx magic-sized clusters with continuously tunable, narrow, and bright emission from blue (λmax = 469 nm) to green (λmax = 550 nm).