Are oxygen-cylinder marking colors standardized worldwide?

The marking colors for oxygen cylinders are not standardized worldwide, which makes the statement true. Different regions and countries may have their own regulations and practices concerning the color coding of gas cylinders, including oxygen. For instance, in North America, oxygen cylinders are typically marked with a green color, but in other countries, it may vary widely, with different hues or combinations used to designate various types of gases.

Additionally, it's important to note that while some manufacturers might adhere to certain color codes for safety reasons, the absence of a universal standard means that divers and professionals must be aware of local regulations and practices to avoid any confusion or mix-ups in gas identification. Understanding the specifics related to your region or the network of manufacturers involved is crucial for maintaining safety in diving scenarios.