Bottom-left panel: NGC 6121 J vs. (B − J_S) CMD for all stars with a membership probability measure. As in Fig. 25, all stars are shown with black dots. We used azure circles, yellow squares, and green triangles to highlight cross-identified stars in the Shokin & Samus (1996) with P_μ ≥ 75%, 2% ≤ P_μ < 75%, and P_μ < 2%, respectively. Bottom-right panel: J vs. P_μ. Top: VPD. We show proper motion error bars for Shokin & Samus variable stars. Star V17 (P_μ = 0%) is not shown because it lies outside the VPD.