Evolution of the g − r colour for EE and non-EE SNe up to 30 days post-explosion. Individual measurements for non-EE SNe are shown as grey points, while pastel-coloured markers represent EE SNe. The solid lines correspond to the centred moving averages, pink for EE and sation for non-EE SNe. Dashed lines indicate the standard deviation (σ) per time bin, and the shaded regions denote the mean ± σ. The vertical black line marks the median upper limit of the EE duration (8 days).