In this study, we report the creation of heterostructured alloy core/shell Ag-In-Zn-S (AIZS)/ZnS quantum dots (QDs) by sequential core-forming, alloying and shelling processes and the fabrication of color-tunable QD light-emitting diodes (QLEDs) with a standard device architecture. Three different (green, yellow, and amber, denoted as G, Y, and A) AIZS/ZnS QDs were successfully prepared at different core-forming, alloying and shelling temperatures and time periods. The QDs were then incorporated into a solution-processed bottom-emitting QLED structure, where the three-colored QD emissive layers (EMLs) are sandwiched in the same structure with ZnO nanoparticles (NPs) and poly(9-vinlycarbazole) (PVK) as electron and hole-transport layers, respectively. The G, Y, and A AIZS/ZnS QLEDs exhibit the highest ever luminance levels of 999, 698, and 498 cd m⁻² and current efficiency (CE) rates of 1.12, 1.17, and 0.36 cd A⁻¹, respectively. Despite the fact that both an appreciable hole barrier and an electron barrier are established in the QD emitting layer (EML) and the hole/electron transport layer, respectively, the three colored QLEDs were successfully activated. Moreover, the electroluminescence (EL) performances of tunable G, Y, and A QLEDs can be distinctly measured using any EL spectrophotometer. The realization of tunable color and moderate brightness as well as the potential all-solution processability using AIZS/ZnS QDs can provide a strong opportunity for future researchers to devise new strategies involving II–VI QD-based QLEDs as a new generation of wide-bandwidth QDs for general lighting applications with high color-rendering indices.