(u−g,g−r) colour−colour diagram for VUDS galaxies used in this study. The points are colour-coded based on the IGM transmission measured from the spectral fitting for each of them. The red points are the galaxies for which GOSSIP+ identified an IGM equal to the mean M06 model. The blue points are the objects for which the IGM transmission is −0.5, −1.0, or −1.5σ below the mean, and green points are for +0.5, +1.0, or +1.5σ above the mean. The galaxies outside the box have an IGM transmission below the mean M06 IGM transmission. Black points represent the whole VUDS sample at 2.7 < z < 3.5.