The aim of this research was to describe the effects of altering the composition of a modified remineralizing agent (MRA) and the osmotic pressure on tooth color by using spectrophotometric analysis. One hundred and four (104) human premolars and molars were randomly divided into 2 groups of 52 specimens each. Group 1 was treated with the remineralizing agent MRA 55, (remineralizing agent 1), a 50% - 50% by weight mixture of coarse-grain and fine-grain generating minerals, and group 2 was treated with the remineralizing agent MRA 91 (remineralizing agent 2), containing the same minerals in a 90% - 10% proportion. Each group was divided into 2 subgroups with 26 specimens each, which were stored as follows: subgroups A were stored in synthetic saliva with isotonic osmotic pressure (IP), and subgroups B in hypotonic osmotic pressure saliva (HP). The initial and final readings were taken with a Vita Easy Shade spectrophotometer. Color parameters (L*, a*, b*) and whiteness indices (WIC, WIO, W) were calculated from the readings. The color changes (deltaL, deltaA, deltaB, and deltaE) and whiteness indices were compared and analyzed with descriptive analyses. The variables deltaL, deltaA, deltaB, deltaE, and the whiteness index W were analyzed with an analysis of variance (ANOVA), and the indices WIC and WIO were analyzed with a nonparametric Kruskal-Wallis ANOVA. The results indicate that combination A2 (MRA 91 and IP) affected variables deltaB and deltaE, while combination B1 (MRA 55 and HP) affected variables deltaA, deltaB and the whiteness index WIO. Only MRA 91 affected the variable deltaL. The osmotic pressure of saliva and the remineralizing agent used affect the color of dental enamel.