RRLs in the color-magnitude diagram color coded with their pulsation period. The first panel shows the RRc stars and the second panel shows the RRab. The color bar represent the pulsation period of the stars and the contours the 68th and 84th percentiles of density of RRL. All models assume M = 0.7 M_⊙. The dotted lines are the theoretical models for the blue and red edge of the instabillity strip of RRc and RRab stars respectively. The solid lines highlight the models that best fit the observations.