Similar to Fig. 11 but for the five colour indices of the UBVRI (Johnson system) of ρ Cas between 1965 and 2017. The (B − V) data points represented by circles are based on a (V − R)/(B − V) relation when no B observations were made (Fig. 11). The arrows and the dates at the top mark eruptive episodes. We note that eruptions preferably take place when the LTV of (B − V) is relatively red, therefore when the star resides in the red part on the HR diagram.