K_s vs. (Z − K_s) color–magnitude diagrams for the region around the red clump position. In the top panel we show data for −6°<l< −2°, in the bottom panel data for the region + 2°<l< + 6°. The dashed lines mark the slope of reddening vectors based on the relative extinctions of the VISTA filters, and assuming the extinction law of Cardelli et al. (1989). Contour lines mark density levels in steps of 5% from the highest density.