Color–magnitude diagram of the center of the Arches cluster. Vertical dashed lines show the color selection used to discard contaminating background and foreground sources. Less extincted foreground sources, mostly associated with the spiral arms, are shown by blue diamonds, whereas intrinsically red objects, such as red giants or red clump stars are marked in red. The location of red clump stars is indicated with an enclosed dotted line. The black diamonds represent likely cluster members. The mean H − K_s color of the bright cluster members, 11 < K_s < 15 mag, in the center of the Arches cluster is shown by a green dot-dashed line. Brighter sources, K_s < 11 mag, belong to the known WR population in the Arches cluster (denoted by the enclosed dashed circle).