CMDs for the selected point sources corrected for Galactic extinction and reddening in the nine HST fields around M 101. Blue, orange, and pink shaded regions indicate selection bins for the young (main sequence and helium burning stars), intermediate (asymptotic giant branch stars), and old (RGB stars) stellar populations, respectively. The region enclosed by red lines represent the selection bin we used for the color measurement only. Dashed lines represent the 50% completeness limits. Photometric errors as derived from ASTs at (F606W − F814W)₀ = 1.0 are marked at (F606W − F814W)₀ = 2.0. We overlaid a 10 Gyr stellar isochrone with [Fe/H] = −1.6 dex in the Padova models (Bressan et al. 2012), to give an indication of the RGB domain in the CMD.