Dear Maytê Mobrige Russo this is an important question of significant practical interest. As you certainly now, titanium dioxide (TiO2) is normally added to concrete in order to fight /reduce air pollution. In most relevant articles the resulting color is not discussed in detail as it is well known that TiO2 is white. According to the useful link cited below "Titanium dioxide is useful for achieving light colors, whites, as well as making light grey when used in grey cement.":