Color−color diagrams for the full population of PCEBs with orbital periods less than 100 d and for a limiting magnitude of g = 15−20 for model αα2. On the left, it shows the u−g vs. g−r diagram, in the middle, the g−r vs. r−i diagram, and on the right, the r−i vs. i−z diagram. The intensity of the grey scale corresponds to the density of objects on a linear scale. The solid line corresponds to the unreddened MS from A-type to M-type MS stars.