Selections of the BSS and RGB samples. Left: near-UV CMD of NGC 1754 within the half-mass radius (r < r_h = 13^′′; gray dots), with the selected BSS sample shown with blue circles and the BSS selection box marked in blue. The rightmost solid line is the evolutionary track for a star of 0.78 M_⊙ (which is the MS turnoff mass for an age t = 12.8 Gyr). The leftmost solid line is the evolutionary track of a 0.98 M_⊙ star. The dashed line is the BASTI isochrone corresponding to a very young age (30 Myr), representing the cluster ZAMS. Right: optical CMD of NGC 1754 for r < r_h=13^′′ (gray dots), with the selected RGB sample shown as red circles and the RGB selection box also marked in red.