Effect of formation redshift on JK_s[3.6][4.5] and HK_s[3.6] color–color diagrams. Top panels: two SEDs of quiescent galaxies are shown. In particular, magenta SED represents a population of 1 Gyr redshifted to z = 3 (i.e. z_form ≈ 6), while cyan line shows SED for a population of 1.5 Gyr redshifted to z = 3 (i.e. z_form ≈ 8). Bottom: color–color plots with evolutionary tracks for star-forming and passive galaxies. Tracks representing star-forming galaxies are shown in blue and cyan and their characteristics are shown in the inserted legends. Two tracks for quiescent galaxies with redshift of formation z_form = 6 and z_form = 8 are shown in magenta and orange respectively. Their e-folding time is τ = 0.1 Gyr and they have solar metallicity.