A single-sheet multi-layer thermal imaging system consists of three layers of color-forming components, which are transformed from a colorless crystalline to a colored amorphous form during the imaging process. The temperature required for the conversion to the colored form is different for each of the color formers. These color-forming layers are separated by thermally-insulating layers that are required for addressing each color-forming layer independently, without any undesired color formation in other layers. The conversion temperatures of the crystalline materials can be altered by incorporation of additional components into the color-forming layers. Such additional components allow the placement of the same color-forming, crystalline material in different layers of the imaging system, eliminating the constraint of its intrinsic melting temperature.