Canary (noun)

1. A small yellow and green finch (Serinus canaria) that is a popular cage bird.
2. A pale yellow or yellowish-green color.
3. A person or thing that serves as an early warning of danger or trouble.

Origin:

From old spanish canaria, from latin canaria, feminine of canarius, from canaria (canary islands), from the indigenous guanche name for the island of tenerife, canaria.

Examples:

1. She kept a canary in a cage in her living room.
2. The walls of the kitchen were painted in a cheerful canary yellow.
3. The canary in the coal mine was the first sign that the air quality was poor.
4. The new security system is like a canary in the coal mine, alerting us to potential breaches.
5. The company's stock is acting like a canary in the coal mine, indicating a broader market downturn.