Pan-STARRS sources in the field of 3C 187 presented in the color-magnitude space. The cluster member candidates are reported with red circles, the other field sources are represented with green circles, and sources from random positions in the sky are plotted in the background with gray dots. The counterpart of 3C 187 core is represented with a magenta circle. The red dashed lines show a linear fit to the selected cluster member candidates, while 90% scatters are represented with black dashed lines.