Traffic lights for pedestrians normally have two main lights: a red light that means 'stop' and a green light that means 'go' (or, more correctly, 'proceed with caution'). There is usually a flashing phase (red in the US, green in Europe) that means 'complete your crossing'. In most locales in North America, the colors used are a red-orange ("Portland orange") for "stop/wait" and a bluish-white ("lunar") for "go." While the "walk" signal is generally a walking human figure, North American pedestrian signals usually show an upraised hand for "stop," while most other countries display a standing human figure. Some older American signals display the verbal commands "Walk" (lunar white or green) and "Don't Walk" or "Wait" (red-orange).
The use of these colors is thought to originate from nautical right-of-way. Usually, the red light contains some orange in its hue, and the green light contains some blue, to provide some support for people with red-green color blindness.
Traffic lights for special vehicles (such as buses or trams) may use other systems, such as vertical vs. horizontal bars of white light. In Portland, Oregon, the tram signals feature a horizontal white bar and an orange vertical bar.
In most countries, the sequence is green (go), amber (prepare to stop), and red (stop). In some systems, however, just before red changes to green, both red and amber are lit. It is customary for drivers to select neutral and/or use the handbrake at red lights; the additional phase is intended to give the driver time to select first gear or release the handbrake before the light turns green, but in practice is treated as an invitation to go before the green light is showing.
In the UK, New Zealand and Canada, amber officially means 'stop (unless it would cause an accident to do so)' but in practice, is treated as 'prepare to stop'. In Russia, Serbia, Austria, Israel, and parts of Mexico, the green light flashes for a few seconds before the amber light comes on. The single flashing amber signal is used in the UK, Ireland and Australia at Pelican crossings. Also it is used in Serbia to mark places where greater attention is needed (dangerous crossings, sharp curves etc.).