Fraction of all galaxies within a particular colour bin that have a LoTSS counterpart down to the flux density limit of LoTSS. The colour of the symbols corresponds with the colour used in Fig. 1. The position along the x-axis is given by the average colour of all the sources in each bin. Poisson error is negligible and the error is dominated by misclassification and incompleteness. The size of the marker is proportional to the number of LoTSS sources matched. This plot demonstrates the additional power of using colour in the LR analysis owing to the much higher probability for red (i − W1 >  3) galaxies to host a radio source than for blue (i − W1 <  2) galaxies to do so.