Asteroid taxonomic classes are taken from NASA PDS. Asteroids are coded by colors which correspond to Tholen classes (SMASSII clases K and L are added) - if Tholen class is not available, it is determined from other classes (Barucci, Tedesco, Howell, SMASS, SMASSII) using Table 1 in S.J. Bus, F. Vilas, M.A. Barucci, Visible-Wavelength Spectroscopy of Asteroids, in Asteroids III.
The most notable feature is compositional diversity of the main belt - increase of primitive classes such as C in the outer belt and the most primitive classses (such as D) in Trojan region.
Pointing cursor out an object will show its name.