g–r colour map of NGC 4565 with values indicated in the bottom colour bar. The dashed black line shows the outermost H I isocontour. The warp is traced with bluer colours in the off-plane regions along the upper-right side of the disk. We can also see the bluer regions, which are less affected by dust, around the truncation (R ∼ 26 kpc). Also, the H I emission follows the optical light distribution.