Proper motion vector diagram of the selected members of ω Centauri (grey dots in all panels) using the astrometry by van Leeuwen et al. (2000). Each panel represents one RGB sub-population with the same colours as in Fig. 2. The solid yellow lines are the mean motion of each sub-population according to Ferraro et al. (2002), while the RGB-MP mean motion is reported as a dotted yellow line in the middle and right panels. The RGB-Mint and RGB-a populations are clearly offset from the RGB-MP one, as was found by Ferraro et al. (2002).