Abstract We are continuing our photometric survey of the trans-neptunian and Centaur populations started in 1997. We report multicolor photometry for 17 objects. With these results combined with previous data (M. A. Barucci, A. Doressoundiram, M. Fulchignoni, D. Tholen, and M. Lazzarin 1999. Icarus 142 , 476–481; M. A. Barucci, J. Romon, A. Doressoundiram, and D. Tholen 2000. Astron. J. 120 , 496–500), we have at our disposal a homogeneous and high-quality set of color indices for 29 objects, numerous enough to make significant studies. The color–color diagrams confirm the wide and continuous spread of colors in the trans-neptunian object population. This diversity may be explained by the combined action of space weathering and collisional resurfacing. We do not find any correlation of colors with size or heliocentric distance, but we note an excess of red objects for perihelion distance greater than 40 AU. Furthermore, our results suggest also that highly inclined (e.g., i >17°) and eccentric objects are preferentially neutral. These objects may have suffered more collisional resurfacing than others.