Have you ever been out for a walk or at a public event and noticed a dog wearing a bright blue vest, bandana, or leash? At first glance, it might seem like a fashionable accessory — a color that looks good in the sun or pairs well with the dog’s fur.

But in many cases, blue gear on a dog is sending an important message.

While there is no legally required color code for service animals in the United States or most other countries, blue has become one of the most commonly recognized colors used by handlers to indicate a service dog or a service dog in training.