Temperature evolution of Flare 1: using the ratio functions R_j, we infer for each time step a flare color temperature by comparing the observed flux ratios with the theoretical black body flux ratios in between two MuSCAT filters using the χ² method. Different ratio functions R_j yield different temperature evolutions. The uncertainty range is indicated by black markers and is valid for all three temperature evolutions. The lines represent the smoothly varying model for the flare color temperature which is derived from the best-fit parameters of the MCMC fitting to the flare light curve using the flare template aflare1. The orange shaded area gives the overlaid uncertainty of all three models.