COLREGs lights and shapes

• Power-driven vessel under way, under 50 m

  Rule 23
  Night:

  Masthead light, sidelights, sternlight.

  Day:

  None.

• Power-driven vessel under way, 50 m or more

  Rule 23
  Night:

  Two masthead lights, the after one higher; sidelights, sternlight.

  Day:

  None.

• Not under command

  Rule 27(a)
  Night:

  Two all-round red; with way on, also sidelights and sternlight (no masthead lights).

  Day:

  Two balls.

• Restricted in ability to manoeuvre

  Rule 27(b)
  Night:

  All-round red, white, red; with way on, also masthead lights, sidelights, sternlight.

  Day:

  Ball, diamond, ball.

• Constrained by her draught

  Rule 28
  Night:

  Three all-round red, in addition to the power-driven lights.

  Day:

  A cylinder.

• Towing, tow 200 m or less

  Rule 24
  Night:

  Two masthead lights in a vertical line; sidelights, sternlight, yellow towing light above the sternlight.

  Day:

  None.

• Towing, tow over 200 m

  Rule 24
  Night:

  Three masthead lights in a vertical line; sidelights, sternlight, towing light.

  Day:

  A diamond, on the towing vessel and on the tow.

• Trawling

  Rule 26(b)
  Night:

  All-round green over white; with way on, also sidelights and sternlight.

  Day:

  Two cones, points together (under 20 m: a basket).

• Fishing, other than trawling

  Rule 26(c)
  Night:

  All-round red over white; gear out more than 150 m: an all-round white towards it. With way on, sidelights and sternlight.

  Day:

  Two cones, points together; cone point up towards outlying gear.

• Pilot vessel on duty

  Rule 29
  Night:

  All-round white over red; under way, also sidelights and sternlight; at anchor, anchor lights.

  Day:

  None in the rules (flag H by the Code of Signals).

• At anchor

  Rule 30(a)
  Night:

  All-round white forward; 50 m or more, a second, lower, aft. Over 100 m, deck lights too.

  Day:

  A ball, forward.

• Aground

  Rule 30(d)
  Night:

  Anchor lights and two all-round red.

  Day:

  Three balls.

• Sailing vessel under way

  Rule 25
  Night:

  Sidelights and sternlight; may add all-round red over green at the masthead.

  Day:

  Under sail and power: a cone, point down.

• Mine clearance

  Rule 27(f)
  Night:

  Three all-round green (one at the foremast head, one at each end of the fore yard); danger within 1,000 m.

  Day:

  Three balls, in the same places.

• Air-cushion vessel, non-displacement mode

  Rule 23(b)
  Night:

  All-round flashing yellow, in addition to the power-driven lights.

  Day:

  None.

A summary for study and quick reference. The official texts (the International Code of Signals, COLREGs and their national versions) govern.