Final answer:
In the United States, when heading towards the sea, the daymarks for the starboard side of the channel are green according to the 'red right returning' navigation rule.
Step-by-step explanation:
Daymarks indicating the starboard side of the channel when proceeding towards the sea are traditionally red in the United States' lateral system of buoyage. Under the 'red right returning' phrase, which is easy to remember, this means when you are returning from the sea, the red marks should be on your right (starboard) side. Conversely, when you are heading towards the sea, the red marks would be on your left (port) side, and the green marks would be on your right (starboard side). Therefore, when a vessel is heading out to sea, the starboard side marks would be green.