Color evolution as measured from the M(400)–M(520) color index vs. rest-frame phase in days. The reference phase of 0 days is the epoch of maximum in the 400 nm band; K corrections and time dilation have been applied. Polynomial fits to the color evolution are shown. The color of SN 2012il close to the peak was evaluated using spectra (see Appendix A for details). All line fits represent third-order polynomials (dashed lines), apart from that for PS1-10ky, which was fitted with a fourth-order polynomial (dotted line).