Color–magnitude diagram of the cluster field. All galaxies with D_proj ≤ 30″ are displayed in red. The seven secure spectroscopic cluster members are marked by black squares (with blue dots for D_proj > 30″) and are all located within a color range 2.6 ≤ z − H ≤ 3.5 (green dotted lines), with an average color of z − H ~ 3. The interlopers found in the above color cut are marked by black crosses. Two simple stellar population (SSP) models for the cluster redshift are overplotted at z − H ~ 3, with solar metallicity and formation redshift of z_f = 5 (red dashed line) or z_f = 3 (blue dashed). The vertical dotted blue line indicates the apparent magnitude of an L* galaxy at z = 1.49, black dashed lines show the 50%-completeness limit.