Distribution of the colour difference (NUV − i) − (NUV − i)_Mod corresponding to the mean distance from typical colour-stellar mass relation of blue cloud (BC) objects for massive (M_star> 10^9.5M_⊙; left), intermediate (10^8.5<M_star ≤ 10^9.5M_⊙; centre), and dwarf (M_star ≤ 10^8.5M_⊙; right) galaxies. The upper row shows the distribution of galaxies observed (black histogram) and detected (grey shaded histogram) by Herschel; the middle and lower rows are the distributions of objects with available nuclear spectroscopy from SDSS (black) with a nuclear star-formation activity (grey) or in a post-starburst phase (grey), respectively. The vertical red and blue dotted lines indicate the limits used to identify the red sequence and the blue cloud.