Upper panels: L1 as a function of the width of the RGB in the c _UBI index (left), the interquartile range of the [O/Na] ratio (middle), and the ratio between CN-strong and CN-weak stars (right). Lower panels: L1 as a function of the R-parameter, which is the number ratio of HB to RGB stars brighter than the HB level (left); the helium abundance inferred by Gratton et al. (2010) from the Iben (1968) method based on the R-parameter (middle); and the fraction of first-population stars (right).