Integrated colloidal photonic crystals with different bandgaps are prepared by molding photocurable SiO2 suspensions and subsequent photopolymerization under UV irradiation. The suspensions show spontaneous crystallization of SiO2 particles and reflect iridescent colors (see figure). The bandgap position is precisely controlled by the particle volume fraction. Such photonic structures can be used as mini-spectrometers in lab-on-a-chip devices, and various optical applications.