Two dual-wavelength (blue and green) light-emitting diodes (LEDs) based on InGaN/GaN multiple quantum wells (MQWs) containing three blue QWs and one green QW next to p-GaN, with different quantum barrier (QB) widths of 12 nm (S-I) and 5 nm (S-II), were prepared. The photoluminescence (PL) and electroluminescence (EL) spectra of LEDs thereof were measured at different temperatures and excitation intensities. The PL results indicate that a decreased width of QB leads to a significant decrease in the quantum-con?ned e?ect (QCE) of the active region, and to a significant enhancement in the effective transport of the carriers from the shallower blue QWs to the deeper green QW, especially at higher temperatures. In contrast, the EL spectrum is dominated by green emissions for both samples due to more injected holes in the green QW than in the blue QWs, and S-I has a greater ratio of blue emission intensity to green emission intensity than S-II, mainly because of the stronger QCE of the active region in S-I than that in S-II. These analyses regarding EL and PL are consistent, and are supported by the experimental observation that S-I has a higher quantum ef?ciency than S-II, due to the stronger QCE and better crystalline quality.