Mass-weighted stellar metallicity gradients (top-left panel) and luminosity-weighted stellar metallicity gradients (bottom-left panel) as functions of the stellar mass of E galaxies. The symbols are red filled circles for CLEs, orange open squares for RQEs, and blue stars for BSFs. Top-right and bottom-right panels: normalized density distributions of mass-weighted metallicity gradients and luminosity-weighted metallicity gradients, respectively, for CLE galaxies (red solid histogram), RQE galaxies (orange open histogram), and BSF galaxies (blue dashed histogram). The integral of each histogram sums to unity. The dotted lines in the panels are gradients equal 0.