A new class of colloidal crystals, whose structural color can be tuned by changing lattice constants, was fabricated. They were composed of polystyrene (PS) submicron particles embedded in a silicone elastomer. The particles were self-assembled into a cubic close packing (ccp) structure, and the ccp (111) planes were parallel to the substrate. These ccp (111) planes produced the structural color of the crystal film by the Bragg's diffraction of incident light. The center-to-center distance between the planes, d was tuned by two approaches. One of the approaches involves the tuning of structural color by increasing d. A composite film fabricated with 202-nm PS particles exhibited a green color; its color changed to red due to the swelling of PDMS elastomer in solvents. On the other hand, a composite film coated on an elastic rubber sheet was stretched horizontally. Therefore, the lattice distance of ccp (111) planes decreased and the wavelength of reflected light reduced as a function of sheet elongation. In contrast, the structural color of the elastic rubber sheet was changed by applying mechanical stress. By tuning the structural color, composite films can be used for optical sensing, thereby avoiding special detector equipment.