A dog wearing a blue vest or harness may look like any other dog, but that simple color often carries an important message that many people overlook.

Blue gear is commonly used for service dogs or service dogs in training, meaning they may be helping someone with vision loss, mobility challenges, seizures, diabetes, PTSD, or other medical conditions that require constant focus.

But blue is only one part of a much bigger system, and misunderstanding the other colors can accidentally put both the dog and its handler at risk.