In this paper, 200 pairs of sphere samples (150 pairs of matte ones and 50 pairs of glossy ones) with a diameter of 4 cm were prepared by a Sailner J400 color three-dimensional (3D) printer to study the applicability of the existing International Commission on Illumination (CIE) color difference formulas (based on two-dimensional colors) to the color difference evaluation of 3D printed sphere models. The colors of these samples are distributed around five color centers (gray, red, yellow, green, and blue) recommended by the CIE. A total of 59 observers with normal color vision aged from 19 to 26 were organized to carry out color difference evaluation experiments by the gray scale method. Eight color difference formulas based on three color spaces, namely CIELAB, CIECAM02, and CAM16, were tested on performance and optimized with the methods of the power function and the lightness factor optimization. The results indicated that the original color difference formulas deliver relatively consistent predictions of the color differences of the 3D printed sphere samples, with a standardized residual sum of squares (STRESS) value of 32.5--34.7. The prediction performance on glossy sphere samples was better than that on matte sphere samples. The F test showed that the performance of the power function method of color difference calculation developed for 3D sphere samples was significantly improved compared with that of the original formulas, with an optimized STRESS value of 24.5--27.3. No significant improvement was observed after k_L optimization.