Peak magnitudecolor evolution relation. Absolute peak magnitudes in the 400 nm band, M(400), vs. the color change from peak to +30 days (rest frame). We define ΔM(400–520)₃₀ = (M₀(400)–M₀(520)) − (M₃₀(400)–M₃₀(520)). The bands at 400 nm and 520 nm are defined in Section 3.2, and the values for ΔM(400–520)₃₀ are reported in Table 1. Left: a plot of eight of the pure sample that have the necessary bands covered in the observer frame to calculate this color term. Right: 11 objects of the complete sample that have the necessary data. The black lines are least-squares straight-line fits to all data in each plot. The red dotted line leaves out CSS121015. The parameters of these line fits are listed in Table 3.