What is the colour of rusty iron filings?

• A. Brown
• B. Blue
• C. Green
• D. White

Answer: (A)

Rust on iron is a reddish-brown color. When iron reacts with oxygen in the presence of water, it forms iron oxide, which coats the surface as rust. This brownish coating is characteristic of rust and contrasts with the metallic gray of unoxidized iron. The other colors describe different materials or metals (blue from copper compounds, green from copper patina, white from various oxides or minerals), so they don’t describe rust on iron filings.