Upper panel: simulated JHK lightcurves adopted from Fig. 8 (sinusoidal fits to the observational data there) with artificial phase shifts of Δφ =  −0.1/0/+0.1 (red, black, and green lines, respectively) imposed in all three filters. Lower panel: resulting variations in an NIR colour − colour diagram, colour coded correspondingly. The labels mark locations occupied by the object at certain phases φ_v, while the arrows designate the sense of rotation of the loops.