In this paper, we utilized the energy-transfer process between upconversion nanoparticles (UCNPs) and organic dye molecules to enhance the upconversion quantum yield (UCQY) of a UCNPs-dye system and tune the luminescence output color. The results indicate that adding an energy dissipation pathway to the energy donor through an energy-transfer process can decrease the ratio of nonradiative transition and cause a new radiative pathway. Through calculation of the rate equations, we studied the effects of the energy-transfer efficiency and activator type on the UCQY enhancement. On the basis of calculations of the CIE color coordinates, tunable color from Er3+, Tm3+, Ho3+, and Tb3+ ions was generated by surface decorating of an organic dye. The approach described here provides a new way to optimize the UCQY and manipulate the emission through energy transfer in a nanoscopic region.