That's an excellent and practical question! When it comes to public trash cans in cities, you'll notice there's often an attempt to use color-coding to guide people. However, a single, universal global standard does not exist. Practices vary significantly by country and even by city.
In many places, you'll find common patterns. Blue is frequently used for recycling, particularly for paper, cardboard, and sometimes mixed containers. Green is often associated with organic waste or general recycling in some regions. Black or gray is overwhelmingly the default color for general waste destined for landfill or incineration.
For instance, in many parts of the United States and Canada, blue lids or bins signal recycling, while black is for landfill trash. In the European Union, while there are directives, colors can differ; yellow might be for plastics in one country and blue for another material. The key takeaway is that local rules always trump any assumed color code. The most important action is to look for the written labels and symbols on the bin itself, which provide the definitive guide for what belongs where. Consistency within a local area is far more crucial than a global standard for effective waste sorting.