Due to their non-toxicity, good light resistance, and weather resistance, inorganic rare earth sulfide colorant materials hold promise for coatings, outdoor displays, and other applications. However, developing additional types of rare earth sulfide colorants and their environmentally friendly preparation processes remains challenging. We have successfully prepared a series of cerium sulfide colorant powders in this study using the hydrothermal method and chemical doping engineering. The effect of La³⁺ doping concentration on the crystal structure and spectral properties of γ-Ce₂S₃ was investigated. The band gap value of cerium sulfide powders increased from 2.12 to 2.22 eV as La³⁺ doping increased. As a result, the color shifts from red to orange-yellow, indicating that La³⁺ doping can alter the chromaticity value effectively. In addition, we have encapsulated the prepared cerium sulfide powders and yellow phosphors with polydimethylsiloxane on a blue chip. The prepared light-emitting device can emit red light with a high degree of purity, which is advantageous for information display and the growth of certain plants. According to the findings, cerium sulfide colorant powders with high spectral modulation and chromaticity values have broad applications in optoelectronics.