UV-optical CMD of iETGs. In the M_r vs. (NUV-r) plane we plot the Wyder et al. (2007) fits to the red sequence (magenta dots and dotted line) and to the blue cloud (cyan dots and dotted line). iETGs with a shell system are indicated with orange dots. KIG 722 is missing from the iETGs sample because no NUV measures are available. The dotted vertical lines provide an indication of the green valley crossing time as a function of the galaxy luminosity (see text). The horizontal error bar accounts for a distance uncertainty of 10%. The vertical error bar accounts for the NUV ZP uncertainty, 0.15 mag (Bai et al. 2015).