B − R vs. H_R(α) plot of all 253 objects. KBOs are represented by solid circles and Centaurs by white dotted solid circles. Objects with separate into two color groups with a “gap” centered at B − R ~ 1.60. Objects with also show statistical evidence of a separation into two-color groups but with a “gap” centered at B − R ~ 1.25. Objects spectra with known features of water ice, methane, methanol, and featureless spectra, are coded using colors as described in the legend. There is no obvious/clear connection between B − R colors and the presence of spectral features.