Final answer:
The color of the rope on the ferry is not mentioned in the provided text excerpts, thus the question cannot be answered based on the information available.
Step-by-step explanation:
The color of the rope on the ferry that prevented people from walking too close to the back edge of the boat is not explicitly mentioned in the provided text excerpts. The passages focus on descriptive elements of the environment and the experiences of the characters in various maritime scenes. While the rich imagery used by the authors embarks the reader on a journey with the characters, the specific detail of the rope color is not provided within these excerpts. Therefore, it is not possible to definitively answer the question based on the given references.