Color-luminosity (left) and color-mass (right) diagrams for MAC0416 cluster galaxies at z ~ 0.4 with spectroscopic redshifts. Cyan data points are the spectroscopic confirmed MAC0416 blue cluster members, representative of the star-forming blue cloud galaxies, while the 76 galaxies used for this metallicity study (Zgals sample) are shown in blue. The red lines and numbers indicate the fraction of Zgals objects (blue symbols) with respect to the parent sample (cyan points). We achieve a uniform coverage at intermediate luminosities/masses. The lowest and highest luminosity/mass bins are under-represented by our sample.