Top panel: observed J − Ks versus i − Ks color−color-diagram of the galaxies shown in Fig. 12 with the same color coding. The Ks magnitude of the galaxies is indicated by the outer shape: triangles for galaxies brighter than Ks* at z = 1.58, inverted triangles for magnitudes between Ks* and Ks* + 2, and circles for galaxies fainter than Ks* + 2. The median color errors for the three magnitude bins are shown in the legend in the lower right corner. The red, green, and blue boxes show the immediate color−color environment of galaxies with a SED consistent with the template spectra at the cluster redshift (Fig. 11) for a passive galaxy (red), a post-starburst template (green), and active starbursts (blue). Bottom panel: background-subtracted cluster galaxy densities in color−color space with density levels of 1 (orange), 2.2 (red), 3.4 (green), 4.6 (blue), 5.8 (dark blue) core cluster galaxies per arcmin² per 0.4 mag in i − Ks per 0.2 mag in J − Ks. Numbers 1−4 mark the central positions for the color−color selection of different galaxy types with the intervals as specified in the text, while the boxes show the template colors as above: 1: passive, 2: transition objects, 3: post-starburst, 4: starburst/starforming.