bow lights

The bi-color ones are not legal. In the USA they are manufactured with a horizontal filament bulb. From straight ahead the light shows orange.

 

To meet the international 72 Colregs there is a pretty precise requirement for range and arcs of visibility. Range is 2 miles. There is an allowable "bleed over" beyond the arcs but it is so small that manufacturers that meet the spec were required to source vertical filament bulbs.

The spec is 112.5 degrees for red and same for green totaling 225 degrees forward. The cutoff between the red and green is very precise so when seen from forward the light changes from red to green.

It is unfortunate because these bulbs have a pretty short lifespan because of the filament configuration.

There are tons of cheap "knockoff" lights that use the standard automotive bayonet type bulbs, none are "legal."

 

As a side note the arcs of visibility apply to the vertical plane too. Thats where you will see "glare shields" or reduced glare lights that have bottom cutoffs to keep the light off the deck and reduce glare that kills night vision.