Peak magnitudecolor evolution relation. This plot illustrates the apparent dependence of peak magnitude on the color and color-evolution rate. The left panel plots the M(400) peak magnitude vs. the color at peak brightness. The right panel plots the same M(400) at peak vs. the color at +30 days (rest frame). The black line fit refers only to the pure sample (2005ap-like objects), the red dot-dashed line fits the extended sample (which includes the 2007bi-like objects), and the black dashed line fits the complete sample.