Significant research has been carried out in ABO 3 perovskites during last decades in tailoring their luminescence properties for advanced optoelectronics. However, research related to exploring contribution of defects, both cation and anion vacancies in photoluminescence for multicolor photon emission has never been explored. Here, in this work, we have harnessed the full gamut of light emission from violet-blue to deep red originating from oxygen vacancies (OVs) in undoped CaSnO 3 (CSO) and Eu@CaO 8 and Eu@SnO 6 sites in the doped CaSnO 3 :Eu 3+ (CSOE) perovskite. Any contribution of Sn 2+ and Eu 2+ , respectively, in photoluminescence of CSO and CSOE has been completely ruled out through Xray absorption near-edge structure. Synchrotron radiation-based extended Xray absorption fine structure and positron annihilation lifetime spectroscopy showed simultaneous distribution of Eu 3+ ions at both asymmetric CaO 8 and symmetric SnO 6 sites owing to a very high negative formation energy value of −6.56 eV for the same. By efficient photon utilization arising from two different charge transfer bands, axial oxygen of SnO 6 octahedra O1 → Eu 3+ CTB (∼250 nm) preferentially transfers energy to Eu@CaO 8 leading to intense electric dipole transition, whereas equatorial oxygen of SnO 6 octahedra O2 → Eu 3+ CTB (∼300 nm) excites Eu@SnO 6 leading to intense magnetic dipole transition. This analogy is confirmed by DFT, wherein it was found that the calculated energy difference between the valence band maxima and conduction band minima is 4.77 eV (∼250 nm) and 4.3 eV (∼300 nm) for Eu@Ca and Eu@Sn sites, respectively. This concept of site-selective excitation and local site engineering can be applied to a variety of optical materials, which provides a unique strategy for tuning other properties of multifunctional crystals that are highly sensitive to the dopant's local environment.