This sketch shows a typical COROT image spot. The analysis of the 3-colour light curves that COROT will gather (thanks to a dispersion device - a prism - mounted in front of the exoplanet channel camera detectors, or CCD’s), will make it possible to distinguish among the different families of detected events (transits, stellar activity, eclipsing binaries).
In fact, planetary transits are achromatic events, while stellar activity – even though still badly known – are expected to be highly chromatic due to temperature variations.