In this study, we demonstrated a monolithic InGaN-based LED to achieve three primary colors of light. Three primary red-green-blue (RGB) colors can be independently obtained from this device at different current densities. This LED structure, which contains three different sets of quantum wells separated with intermediate carrier blocking layers (ICBLs), was grown by metal-organic chemical vapor deposition (MOCVD). Results show that this LED can emit light ranging from 460 to 650 nm to cover the entire visible spectrum. In addition to three primary colors, many other colors can be obtained by color mixing techniques. Based on this novel structure, we also achieved, for the first time, a monolithic white-light LED with tunable color-temperatures from 2700 to 6500 Kelvin (K). To generate white light, a full-color LED (or tricolor LED) is operated under pulsed conditions with each pulse consisting of multiple steps of different current amplitudes and widths emitting different colors. The combined spectrum of different colors is aimed to mimic that of the blackbody radiation light source. The pulse rate is designed to be higher than the human eye response rate, so the human eye will not discern the emission of successive colors but a singular emission of white light. Results of a two-step pulse design show this method is able to generate white light from warm color temperature (2700 K) to cold color temperature (6500 K).