Comparison of integrated [B–R] colour of centaur 523676 (2013 UL10) (continuous black line) with respect to the colour derived in concentric annular regions with increasing distance from the optocentre (dots). Each dot represent the [B–R] colour derived in the annulus between that ρ value andthe preceding one. The blue and red dashed areas indicate lower and upper limits of the [B–R] colours of the blue and red inactive centaur groups, respectively, when adopting a gap at [B–R] = 1.50. The yellow dot-dashed line indicates the [B–R] colour of the Sun. The vertical dashed line indicates the considered limit for the nucleus (FWHM).