The purpose of this study was to test whether prosthetic treatment with different intraradicular posts influences the color of the buccal gingiva at teeth restored with zirconia crowns. A total of 31 patients in need of a full-coverage single crown at an endodontically treated premolar, canine, or incisor in the maxilla or the mandible were included. The patients were randomly assigned to receive composite build-ups using titanium (Ti), zirconia (Zi), or glass-fiber (Gf) posts or a build-up using no post at all (NP). All the teeth were restored with veneered zirconia single crowns. Spectrophotometric color measurements of the buccal gingiva were taken at the test teeth prior to and after the prosthetic treatment, and at the contralateral vital control tooth. The differences of the color components ΔL, Δa, and Δb and the total color difference ΔE between the test tooth prior to and after treatment and between the test and control tooth were calculated. The color differences were analyzed to determine whether they varied from 0 and 3.7, the threshold for detection by the human eye. Analysis of variance was performed to compare ΔE, ΔL, Δa, and Δb in the four post groups. The prosthetic treatment induced a significant color change ΔE in all the groups (Ti: ΔE1 = 6.4 ± 1.9; Zi: 7.1 ± 2.0; Gf: 6.2 ± 3.5; NP: 6.6 ± 3.5). There was no significant difference between Ti, Zi, Gf, and NP with respect to ΔE, ΔL, Δa, and Δb. Gingival color ΔE differed significantly between the test and control teeth before (Ti: ΔE = 6.8 ± 3.0; Zi: 9.0 ± 3.5; Gf: 5.7 ± 2.1; NP: 8.2 ± 2.8) and after prosthetic treatment (Ti: ΔE = 6.0 ± 2.8; Zi: 7.1 ± 2.9; Gf: 7.2 ± 3.0; NP: 6.9 ± 2.6). The use of different intraradicular posts (titanium, zirconia, glass fiber) or no post at all did not influence the color of the buccal gingiva at teeth restored with zirconia crowns. There was a significant gingival color difference between endodontically treated teeth and vital control teeth, both before and after prosthetic treatment.