What type of buoy is designated by odd numbers and green color?

The type of buoy designated by odd numbers and a green color is indeed a nun buoy. Nun buoys are used in the maritime system to mark the right side of a channel when entering from the sea, and they adhere to the IALA (International Association of Lighthouse Authorities) buoyage system. They are typically conical in shape, and their green coloration along with odd numbering serves as a visual indication for navigators to keep them on their right when approaching a harbor or navigating a waterway.

In the context of the options provided, cylindrical buoys, mooring buoys, and safe water buoys refer to different functions and designs. Cylindrical buoys often indicate navigable water but are not specifically tied to a color or numbering of odd numbers. Mooring buoys serve to provide a location for vessels to anchor, while safe water buoys are marked with a red and white stripe indicating safe passage which does not correlate with the odd-numbered green buoys. Thus, the significance of odd numbers and green color specifically points to nun buoys in navigation.