Left: zoom-in of the left-panel CMD shown in Fig. 1 around the region where binaries with large mass ratios can be more clearly distinguished from the bulk of single stars. Right: simulated CMD including single stars only. Simulated cluster members and field stars are shown as black points and magenta starred symbols, respectively. The red and green lines in both panels enclose region A of the CMD, used to infer the binary fraction. The grey shaded area delineates region B, a sub-region of A that primarily hosts binaries with mass ratios larger than 0.5. Region F, populated by field stars, is the CMD area enclosed by the dashed black lines.