Upper panel: CMD of NGC 6752 HB stars from Momany et al. (2002). Lower panel: one synthetic realisation of the cluster HB, with the same number of stars as observed. Open circles denote FG stars, filled triangles SG stars with Y = 0.254, open squares SG stars with Y = 0.273. The vertical lines define the boundaries of the three boxes in which the observed CMD has been partitioned. The location of the reddest vertical line coincides with the location of the Grundahl’s jump (see text for details).