🟦 ATON (Aids to Navigation) Color-Coded Cheat Sheet
The “Road Signs of the Water” — Simple, Clear, and ICW-Friendly
RENT = Red Even Nuns Triangle
COGS = Cans Odd Green Square
🟥 Red Markers
“RED RIGHT RETURNING”
Shape: Nun (cone)
Numbers: Even
Lights: Red flashing
Meaning:
- Keep on your right (starboard) side when returning from sea
- Keep on ICW starboard (if it also has a yellow triangle)
- Red markers mark the right side of a channel
What you see:
🟥 Nun buoy, red dayboard, or red light
🟩 Green Markers
Opposite of red
Shape: Can (cylinder)
Numbers: Odd
Lights: Green flashing
Meaning:
- Keep on your left (port) side when returning from sea
- Keep on ICW port if it has a yellow square
What you see:
🟩 Can buoy, green dayboard, or green light
🟨 ICW Yellow Overlays
Used ONLY on the Intracoastal Waterway (ICW).
Yellow Triangle (▲)
- Treat as red on the ICW
- Keep on starboard when following ICW direction
(typically southbound on the East Coast)
Yellow Square (■)
- Treat as green on the ICW
- Keep on port when following ICW direction
Important: ICW markings override the normal red/green “returning from sea” rule when you’re following the ICW path.
⚠️ Regulatory & Information Markers (White with Orange)
⭕ Controlled Area
- No Wake
- Speed Limit
- Slow Speed / Minimum Wake
▲ Danger
- Shoals
- Rocks
- Wrecks
- Unmarked hazards
⧈ Keep Out
- Swim zones
- Dredging areas
- Wildlife protection areas
🔳 Information / Guidance
- Directions
- Marina names
- Docking tips
- Mile markers
🟦 Safe Water / Mid-Channel Aids
⚪ Safe Water Marker (Red & White Vertical Stripes)
Meaning:
- Safe water all around
- Often marks:
- Mid-channel
- Fairways
- Beginning of channels
Light: White
🟫 Special Purpose Markers
Solid yellow
Used for:
- Military areas
- Fish traps
- Cables
- Diving areas (sometimes)
Not used for channel navigation.
🟧 Mooring Buoy
White with blue horizontal band
- The ONLY buoy you may legally tie up to (other than your own dock)
⚓ Preferred Channel Markers (Junction Buoys)
These show which side of a split channel is preferred.
🔴🟩 Red over Green (top color = preferred)
- Red over Green → Red is top → Preferred channel is to the RIGHT
🟩🔴 Green over Red
- Green is top → Preferred channel is to the LEFT
🌙 Lights on ATONs (Quick Guide)
| Light Color | Meaning |
|---|---|
| 🔴 Red light | Red side of channel |
| 🟢 Green light | Green side of channel |
| ⚪ White light | Safe water buoy / Range light / Marker |
| 🔶 Yellow light | ICW aids or special purpose |
Flash patterns can identify the marker’s number and position, but color is what matters most for small boating.
🛥️ Quick 5-Second Memory Version
- Red = right returning
- Green = left returning
- Yellow triangle = treat like red on ICW
- Yellow square = treat like green on ICW
- White with orange = warnings/regulations
- White + blue stripe = mooring only