CoRoT and Spitzer colour vs. time relations. Top to bottom: CoRoT–[3.6], CoRoT–[4.5] and [3.6]–[4.5], with residuals immediately below in each case. Black points show data used in the spot modelling, orange points indicate data that was masked in the fit and the cyan line represents the colour signature of the spot model. All colour-time relations display quasi-sinusoidal variations, which can most clearly be seen comparing the widely separated bandpasses of the CoRoT–[4.5] colour space. All plots share common axes.