Highly fluorescent excited-state charge-transfer complexes (exciplexes) formed at the interfacial region between a polymeric donor matrix, here, poly(N-vinylcarbazole), and embedded nanostructured acceptors are characterized for their photophysical properties. Exciplex-to-exciton emission switching is observed after solvent vapor annealing (SVA) due to the size evolution of the nanostructures beyond the exciton diffusion length. Color-tunable exiplex emission (sky blue, green, and orange) is demonstrated for three different nanostructured acceptors with the same HOMO-LUMO gap (i.e., the same blue excitonic emission) but with different electron affinity. White-emitting poly(N-vinylcarbazole) film is also fabricated, simply by incorporating mixed supramolecular acceptors, which provide independent exciplex emissions. This study presents important insights into the excited-state intermolecular interaction at the well-defined nanoscale interface and suggests an efficient way to obtain multicolored exciplex emissions.