Density surface and distribution of rest-frame colours for galaxies from the ALHAMBRA survey obtained using EMILES+BaSTI SSP models. Top: rest-frame intrinsic colours (m_F551 − J)_int (X-axis) and (m_F365 − m_F551)_int (Y-axis) after correcting for extinction at different redshifts. Bottom: rest-frame colours without removing dust effects. Redder (bluer) density-curve colours are related to higher (lower) densities. Inner panels, histograms of the intrinsic (top) and observed (bottom) rest-frame colour m_F365 − m_F551. Dashed lines in the top panels illustrate our limiting value (m_F365 − m_F551)_int = 1.5 for quiescent galaxies, and in the bottom panels the quiescent UVJ sample defined by Moresco et al. (2013, Eq. (1)). Black dots are galaxies labelled as quiescent by the UVJ criteria of Moresco et al. (2013) that lie in the star-forming region after removing extinction effects. We illustrate the colour variations due to a reddening of A_V = 1 (black arrow), assuming the extinction law of Fitzpatrick (1999).