Navigation and Seamanship

1.4.5.22. Colour shading

Modern charts have a system of colour shading to give greater emphasis to certain depths. This is particularly the case with inshore soundings. Shallow waters are usually indicated by deep blue colouring (green if they are dry at low tide), which fades out to paler blue as the water becomes deeper. The land is often shaded yellow .Navigation lights, which are the navigator's signposts, as it were, are indicated by a red 'flash'.