Photometric selection of MPs in the wide-field dataset. Top panel: (I, C_U, B, I) CMD of NGC 3201. Data from Stetson et al. (2019). The red and blue lines are the two fiducial lines at the edge of the RGB used to obtain the verticalized C_U, B, I distribution. Bottom panel: histogram of the verticalized C_U, B, I distribution. The red and blue curve are the two best-fit Gaussian used to select the FP and SP stars, respectively, while the black one is the sum of the two.