B − V colour curve of SN 2021tsz compared to those of the comparison sample SNe. The colour of SN 2021tsz and the comparison sample are extinction corrected. Prior to estimating the colour, LOESS regression was applied to smooth out the B and V band light curves of all SNe. In the background, the unreddened sub-sample of 19 SNe II from de Jaeger et al. (2018) is shown in blue, while the rest of the sample SNe with extinction correction applied are shown in pink.