While the width-luminosity relation ( WLR ) among type Ia supernovae ( slower is brighter ) is one of the best studied properties of this type of events , its physical basis has not been identified convincingly . The ’ luminosity ’ is known to be related to a clear physical quantity - the amount of ^ { 56 } Ni synthesized , but the ’ width ’ has not been quantitatively linked yet to a physical time scale . We show that the recombination time of ^ { 56 } Fe and ^ { 56 } Co from doubly to singly ionized states causes the typical observed break in the color curve B-V due to a cliff in the mean opacities , and is a robust width measure of the light curve , which is insensitive to radiation transfer uncertainties . A simple photospheric model is shown to predict the recombination time to an accuracy of \sim 5 days , allowing a quantitative understanding of the color WLR . Two physical times scales of the width luminosity relation are shown to be set by two column densities- the total column density which sets the gamma-ray escape time t _ { 0 } ( previous Paper I ) and the ^ { 56 } Ni column density which sets the recombination time ( this Paper II ) . Central detonations of sub- M _ { ch } WDs and direct WD collision models have gamma-ray escape times and recombination times which are consistent with observations across the luminosity range of type Ia ’ s . Delayed detonation Chandrasekhar mass models have recombination times that are broadly consistent with observations , with tension at the bright end of the luminosity range and inconsistent gamma-ray escape times at the faint end .