Rule 25

	Sailing vessels may show just a tricolour light. This:Reduces power consumption. Aids visibility of the lights in large waves. Lights up a masthead wind indicator. Removes the backscatter at the bow.
All vessels should have more than one set of lights, in case of failure. A vessel of less than 20m may use a bicolour side light.
	A vessel over 20m must have separate side lights.
Any sailing vessel may show two all round lights at the masthead. The upper red and the lower green. This enables the boat to be seen in rough weather, but is only usually used by large vessels because of the power use.(RED OVER GREEN-SAILING MACHINE)
	A vessel motor sailing, is a power-driven vessel under the rules. To indicate that she is motoring she must display a cone point downwards.
At night always take a torch with you in a dinghy. If a vessel is travelling fast, they will not see you in sufficient time, if you do not show a light. Take a torch ashore, even if it is still light, if there is any possibility of returning after dark.

It may help to remember that sailing vessels never show a white steaming light. So, if you see a vessel showing only a red or green light, it must be a sailing boat.

Of course, from the stern you can not tell a sailing vessel from a power-driven one, why does this not matter? (Rule 13).

It is useful to be able to show a tricolour light when sailing, but it must be turned off when you start to motor. If it is left on, you are indicating that you are a trawler or a fishing vessel other than a trawler, this is probably the most commonly seen error in the lighting of vessels.

Test on Rule 25.