Selection effects in the M87 and Milky Way samples. Top: Optical CMD for M87 GCs in fields 1, 2, and 3, as in Fig. 3. The open circles represent sources that are detected only in the WFPC2 optical frames, while the filled circles represent sources also detected in the far‐UV. Bottom: Color‐color diagram for M87 clusters with ﹩V_{0}< 24.1﹩ (circles, far‐UV detections; arrows, upper limits) and Milky Way GCs (triangles). The dividing lines are explained in the text. For reference, the 100% far‐UV completeness line at ﹩V_{0}=22﹩ corresponds to ﹩M_{V,0}=-9.1﹩.