Difference between redshift assignments as a function of the SALT2 fitted colour, for synthetic core-collapse events (blue dots) and data events (all other symbols), after all selections previous to that on SALT2 X₁ and colour (see text). Green circles (resp. red triangles) are data events present in our sample which have been identified as Type Ia (resp. core-collapse) supernovae by spectroscopy. Open black circles stand for data events with no spectroscopic identification.