The B band light curve a) and the time evolution, in the observer frame, of the color indices b) of the OA of GRB 060218 (UVOT data). The points are connected by lines for convenience and may not precisely reflect the complicated profile of the variations in the data gaps. The data were corrected for the reddening and light contribution of the host galaxy as described in Sect. 3. (This figure is available in color in electronic form.)