The R-band light curve of 4C 38.41 in 1995–2011 (top panel). Blue dots indicate the data used to derive the B − R colour indices shown both as a function of time (middle panel) and as a function of magnitude (bottom panel). The black dotted and blue dashed lines in the top panel indicate the average magnitude for the whole dataset and the data used for the colour indices, respectively. In the middle panel, the blue dashed line marks the average colour index.