Δ_{C F275W, F336W, F438W} vs. Δ_{F275W, F814W} ChMs for NGC 6791 (left) and NGC 1783 (right). In both panels the orange points in the bottom left corner indicate the distribution expected for a simple population derived from ASs, while the orange ellipses encircle the 68.27% of simulated points. The Δ_{F275W, F814W} kernel-density distributions of observed and simulated stars are shown in black and orange, respectively, in the top panel of each figure. The insets show a comparison between the ChMs of the two simple-population clusters and that of the metal-rich GC NGC 6624 (Milone et al. 2017).