Template light curves for the four thermonuclear supernova types at z = 0.5. The upper panel shows the R light curve for the Ia-normal subtype as solid (black), the Ia-faint subtype as dash-dotted (blue), the 91T-like subtype as dotted (green) and the 91bg-like subtype as dashed (cyan). In the lower panel the R−I colour evolution for the four subtypes is shown using the same line styles (this figure is available in colour in the electronic version of the article).