Time evolution of the V − I, B − J, and B − H color and the D₄₀₀₀ index for a stellar population of Z_⊙/5 forming at a constant SFR, according to a Salpeter IMF that is truncated above M_up = 3, 2.5 and 1.9 M_⊙ (red, green and blue, respectively), corresponding to a migration timescale τ_m of SF clumps from the disk of, respectively, 0.64, 1 and 2 Gyr. Predictions for a fully populated (0.1−100 M_⊙) Salpeter IMF for a constant and exponentially decreasing (τ1) SFR are shown with the gray solid and dashed curve, respectively.