what does a no power boat ahead sign look like

As fast as possible

Slow down and turn to avoid the small boat ahead of you.

when its safe and no one ahead

When you face the front of the boat, the left side is the 'port' side and with a red light, the right side is the 'starboard' side with a green light. A boat approaching you from ahead would see your green light on the left and red on the right, the same as you would see his lights. Possible collision ahead!