This paper presents a binary-star study for the color-magnitude diagrams of 12 globular clusters, in
which each star is assumed to be distinguishable. It shows that the CMDs of star clusters can be
explained well via binary-star populations, although some differences are shown when comparing
observational and theoretical CMDs. As a result of the study, some basic properties, i.e., stellar
age, metallicity, distance modulus, and color excess, are determined for the 12 sample clusters. The
sample clusters are shown to be old (Age ≥ 8.4 Gyr) and metal poor (Z ≤ 0.01). When we compare
the cluster properties determined by binary- and single-star stellar populations, respectively, it shows
that the two types of population models can give different results for star clusters. Because binary
stars are common, the study suggests using a binary method to study the CMDs of star clusters. It
also suggests modeling the stellar populations of star clusters via binary stars.