Room temperature phosphorescence (RTP) materials are widely used in various fields. However, the realization of multicolor RTP via facile approaches still remains a great challenge. In this study, we propose an in situ hydrolysis method using different solvents to synthesize blue, green, and yellow phosphorescence ZnO/SiO2 composites. By investigating the photoluminescence (PL) and phosphorescence mechanisms of ZnO/SiO2 composites, it is discovered that the solvents not only introduce impurities to ZnO but also affect the position of defect energy levels, leading to the variation in luminescent performance. Meanwhile, the as-synthesized ZnO/SiO2 composites exhibit stable PL and phosphorescence under extreme conditions. Specifically, the PL and phosphorescence properties of the composites are well maintained at high temperature (523 K) or underwater. Owing to the multicolor phosphorescence properties of these ZnO/SiO2 products, herein, we demonstrate that ZnO/SiO2 composites can act as new smart materials for information encryption, fingerprint identification, and white light-emitting diodes (WLEDs).