Top: R − z color–magnitude diagram of the cluster environment based on the FORS 2 imaging data. The richly populated cluster red-sequence around the median ridgeline color R − z  ~  2.05 (red dashed line) is clearly visible. Filled red circles indicate objects within a 30″ radius from the X-ray center, green circles correspond to 0.5−1′, small black dots represent all other objects in the field, and open circles mark spectroscopically confirmed cluster members. Horizontal dotted lines define the applied color cut interval of  ± 0.2 mag about the median color, while the dotted vertical line refers to the expected apparent magnitude (m∗   ≃  21.9 mag) of a passively evolving L∗  galaxy at the cluster redshift (in both panels). The 50% completeness limit is indicated by the black solid line. Bottom: histogram of galaxy counts in the red color interval 1.85  ≤  R − z  ≤  2.25 in bins of 0.4 mag for galaxies within 1′ from the cluster center (blue line). The vertical solid line indicates the nominal 50% completeness limit of the data, while the black dotted line shows the magnitude distribution for galaxies at larger distances for comparison.