Maximum colour variation BP-RP versus the corresponding G-band variation as observed in the Gaia DR3 light curve. Top: all our targets are represented and the diagram is colour-coded by the ratio G mean flux to its standard error (RFG). For comparison, we represented the effect of a 2 mag visual interstellar extinction with a grey arrow. The reddening effect occurring during RCB stars’ photometric declines is on average two times higher. Bottom: zoom on the targets with the least variation (∆G < 0.5 mag) colour-coded with their types.