B vs. [B−I] colour−magnitude plot of V1118 (left) and V1143 Ori (right). In the left panel open circles (in blue) refer to our data still unpublished (Giannini et al., in prep.). Solid circles (black and red) refer to the present data. Green circles are given for comparison purposes and refer to a recent outburst of V1118 monitored by Audard et al. (2005). In the lower-left corner the arrow indicates an extinction of A_V = 1 mag, according to the law by Rieke & Lebofsky (1985).