Why the starboard side light is green and how it helps mariners stay safe at night.

Outline in my head, just so you can follow along:

• Start with a human moment at dusk on the water and reveal the color fact: starboard light is green.

• Explain the color code behind those lights, in plain language.

• Share how to read the lights in common situations and why it matters for safety.

• Add a short side note about other lights you’ll see on vessels and what they mean.

• Include a couple of real-life-style digressions that still circle back to the main point.

• End with a simple recap and a friendly nudge to stay curious on the water.

Green on the starboard side—that’s the quick answer

At night or in fog, a ship doesn’t need to wink to tell you where it’s headed. It uses color. And the color you’ll notice along the vessel’s side is green on the starboard (the right-hand side) and red on the port side (the left). The rule is clean and practical: green means “starboard,” red means “port.” White lights play a role too, but those two colors are the quick map you’ll rely on when you’re skimming through the dark.

Why COLORS matter in the Rules of the Road

Think about it like a traffic signal at sea. Roads have signs to guide you; oceans have lights. The COLREGs—the International Regulations for Preventing Collisions at Sea—set this color system so you can figure out a vessel’s orientation in a glance, even when visibility is poor. It’s not ornamental. It’s safety gear you wear as a mental reflex.

A short tour of the color code

• Green sidelight: starboard side (the right side of the vessel). It’s one of the most recognizable cues in the night.

• Red sidelight: port side (the left side).

• White lights: there are a few varieties here, including a stern light and masthead/light configurations seen on many ships. They act like backlit markers, helping others judge a vessel’s position and motion behind and ahead.

If you’ve ever wondered why ships look like they’re wearing a two-tone glow, this is it: the red and green are like the eyes of the ship—telling you where it’s coming from, and which way it’s headed as it crosses the water.

Let me explain how the colors help in real life scenarios

Imagine you’re cruising near a busy channel. A vessel appears ahead, its red light faint against the horizon. That red tells you, in a flash, which flank of the other ship you’re near. If their green sidelight catches your eye, you know you’re seeing their starboard side. That single color cue invites a mental map: “Okay, they’re on this side of my path.” Now you can judge distance, speed, and potential crossing angles without needing a long radar reading or radio chatter.

And what if you’re heading toward another boat head-on, or you’re overtaking someone? The colors, plus the white lights, start to form a more complete picture. The rules say who should alter course or slow down to avoid a close call. You don’t want to be the one guessing in the dark. You want that quick, universal language—green on the right, red on the left, white lights to mark positions—and you want to respect it, even when the sea is choppy and time feels tight.

A friendly tangent: the other lights you’ll notice

Besides the classic red and green sidelights, vessels carry white lights that help define their presence and maneuvering. A forward white light or a masthead light can tell you a lot about a vessel’s direction and speed, especially when you’re closing in from behind or when visibility is compromised. Some small boats might tuck away lights, or use reflective gear, but the big metal ships keep to the standard palette. It’s like a language you learn by listening for the sounds around you—the color cues are the spoken words.

Something to keep in mind: interpretation, not assumption

Color alone doesn’t tell the whole story. It’s part of a bigger picture that includes distance, bearing, speed, wind, current, and the other vessel’s course. The lights give you a snapshot; your understanding comes from stitching that snapshot with what you’re doing with your own vessel. It’s a dialogue—one that demands attention and respect.

A few quick, practical tips for navigating by lights

• Always scan for sidelight colors first, then fill in the rest with other indicators like the white lights and the vessel’s moving pattern.

• When you’re unsure, slow down. It buys you time to see more lights, hear a sound signal, or communicate if needed.

• Don’t rely on one clue alone. If you spot a green light, check for a corresponding white light that confirms motion and direction. If something looks off, assume the worst and adjust.

• In fog or rain, lights become even more critical. Maintain a safe speed and increase your vigilance so you can react to the next glimmer on the horizon.

A tiny digression that still fits here

There’s something almost cinematic about night navigation. You’re not just watching for objects; you’re watching for intent. A vessel’s color-coded glow acts like a cue in a silent play: I’m here, I’m moving this way, and I’ll likely shift course soon. It’s oddly comforting to know that a rule as simple as green on the right can help you predict behavior in the vast, confusing sea. And yes, it does feel a bit like learning a new language—one that could save a life.

How to remember it without turning it into a quiz ritual

• The phrase “Green on the right” is a quick, memorable anchor.

• Red on the left is your second cue. Put the two together and you have a mental compass for other vessels.

• White lights are the supporting cast—identify where they sit so you can fill in the whole scene: who’s coming, who’s going, and who’s overtaking whom.

Why this matters for anyone who spends time on the water

Waterways are busy, even when they look calm from shore. Boats, ferries, fishing crews, and pleasure craft all share the same rulebook. When you can read those lights at a glance, you reduce the chance of a misread or a near miss. The colors aren’t just decoration; they’re guardrails for the night, a simple system that helps everyone move more predictably through shared space.

A practical mental map you can keep handy

• Starboard side = green light on the right.

• Port side = red light on the left.

• White lights indicate the rearward or forward presence and movement of a vessel, providing context about where the boat is heading.

• In tight quarters or poor visibility, slow down, observe, and communicate using standardized signals if needed.

A closing thought to anchor the idea

Here’s the thing: you don’t have to memorize a hundred rules to stay safe. Start with the basic color code, then let that knowledge grow with experience and curiosity. The sea is a dynamic classroom, and these lights are its simplest, most reliable teaching tool. When you understand what you’re looking at, you’re not just following a rule—you’re reading a living map that helps you stay clear of danger and move confidently through the water.

A concise recap

• Green sidelight marks the starboard (right) side of a vessel.

• Red sidelight marks the port (left) side.

• White lights provide additional orientation, especially when ships are moving or turning.

• Reading these lights quickly helps you infer relative position, heading, and potential actions—crucial for safe navigation, especially after dark or in poor visibility.

If you’re ever unsure about a light’s meaning, the safest move is to give yourself time and space. The water is a shared space, and the colors exist to keep it that way. So next time you’re near a channel at night, take a moment to notice the greens and reds, listen for a sound signal if one seems due, and let that color code guide your decisions. You’ll notice the water feels a little more navigable when you let the lights do a portion of the thinking for you.

And that’s the essence: color tells a story. Green on the starboard side tells you the right-hand path. Red on the port tells you the left. White lights fill in the rest, helping you read the scene with confidence. It’s a small system, but it carries big responsibility—and it works best when you stay curious, vigilant, and respectful of the rules that keep mariners safe from horizon to horizon.