Light curves of ϕ Dra in 11 photometric colours with effective wavelengths from 350 to 770 nm (on the right) plotted versus the new ephemeris with zero phase at the maximum (Eq. (3)). Grey full lines are the fits calculated by the simple model of ϕ Dra light variability (Eq. (1)). Light curves are vertically shifted to better display the light variability. Areas of individual symbols are proportional to the weight of the measurement.