The controllable growth of self-organized 3D semi-polar faceted GaN islands is reported, which performs as an ideal template for the fabrication of semi-polar InGaN/GaN light-emitting quantum wells on the sidewalls. Special transmission electron microscope (TEM) sample preparation is employed to analyse the microstructure and growth mechanism of the multi quantum wells on the sidewall facets. Together with cathodoluminescence, the results show that the mixed white light (blue, green and red) emission in a single island can be achieved and the semi-polar faceted InGaN/GaN quantum wells act as the main region for the bright multi-color light emitting. Further optimization of the facet structure will improve the flexibility of light emission and provide a new method for the next generation of white lighting.