RGB images obtained with the WFC/INT (left) and ACAM/WHT (right) g′, r′, and i′ frames of the SZ sources PSZ1 G063.92−16.75 and PSZ1 G158.34−47.49, respectively. The squares indicate the corresponding SZ Planck coordinates, while the arrows point to the blue gravitational arcs detected in the core of the clusters. The circle is a 1.2′ radius region including the brightest galaxies of each cluster.