Density surface and distribution of stellar mass vs. rest-frame colour (m_F365 − m_F551) for galaxies from the ALHAMBRA survey using BC03 SSP models. Top: rest-frame intrinsic colour (m_F365 − m_F551)_int (Y-axis) after correcting for extinction at different redshift. Bottom: rest-frame colours without removing dust effects. Redder (bluer) density-curve colours are related to high (low) densities. Dashed green lines in the top panels illustrate the limiting value (m_F365 − m_F551)_int = 1.5 used for selecting quiescent galaxies in Sect. 4.1. Dashed and solid red lines show the fit to the quiescent sequence, , and the limiting intrinsic colours, , values of quiescent galaxies respectively (see details in Sect. 4.2). Black dots in the bottom panels are galaxies labelled as quiescent with the UVJ criteria of Moresco et al. (2013) that lie in the star-forming region after removing extinction effects.