g − r colour of the three pre-SN outbursts or activities for which multi-band photometry is available. The phases are relative to the maximum in the r-band, which was derived from a Gaussian fit over the data points. For comparison, the V − R colour of the 2000 and 2008 outbursts of the known LBV AT 2000ch (Pastorello et al. 2010) and of the SN impostor SN 2007sv (Tartaglia et al. 2015) are also shown. The g − r colour of the outbursts is red, around g − r∼0.5 mag.