range of chemical compositions, that include consistently the effect of radiative levitation. The underlying assumptions are that [*(i)*]{} the HB model evolutionary lifetimes, [*(ii)*]{} the evolution of ${\rm T_{\rm eff}}$ and [*(iii)*]{} bolometric luminosity, and [*(iv)*]{} the structure of the corresponding model atmospheres are not affected by the radiative levitation, and that the relevant bolometric corrections are determined mainly by the enhanced metals. With these assumptions the effect of radiative levitation on bolometric corrections makes $m_{F160BW}$ fainter by about 0.15 and $m_{F336W}$ and $m_{F555W}$ brighter by about 0.1 and 0.05 respectively. Paper I has shown how this approximation allowed us to recover the three different He-abundances inferred by the multimodal MS, along the blue HB of NGC2808. We are therefore confident that a similar procedure will be adequate to constrain the He distribution along the HB of these three clusters, that we are going to discuss separately in the following section.

The synthetic HB simulations
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The theoretical analysis performed in this paper is based on synthetic HB calculations, performed as described in Paper I. The analysis of NGC2808 was simplified by the fact that the initial He content of the cluster subpopulations is somewhat ’quantized’, as shown by the 