That's a great question! While there's no single global standard, certain color conventions have become widely adopted in public waste management. The most common standard you'll see in many cities, especially across North America and Europe, is green for general municipal waste and blue for recycling.
This green-and-blue system helps create instant visual recognition. The green bin is for everyday trash destined for the landfill or incineration. The blue bin is typically for clean, dry recyclables like paper, cardboard, plastic bottles, and metal cans. Many cities are expanding this system with additional colors: brown or black for organic/compostable waste is becoming increasingly common.
However, it's important to remember that local rules always apply. In some regions, you might find gray or black for general waste. Orange bins are sometimes used for plastic recycling specifically. The key trend is toward color-coding to simplify waste sorting for the public and improve the efficiency of collection and processing. So next time you're in a city, take a look—the colors are a small but important part of keeping our urban environments clean.