What type of a property is the color of rust?
The color of rust is a physical property.
The important difference between physical and chemical properties is the fact that you can observe physical properties without changing the identity of the substance or object.
This cannot be said for chemical properties, which can only be observed when a substance reacts with another substance, being fundamentally changed in the process.
In this case, the red color of rust is a physical property because you don't have to do anything to the rust to observe its color. Once rust if formed, you can observe its reddish color without chaning the rust in any way.
Color in general is cinsidered a physical property.
On the other hand, the ability to rust is a chemical property of iron. Iron reacts with oxygen to form a combination of iron oxides, which is characteristic of a chemical change.
The iron metal that you started with no longer exists in that form. Once it rusts, it exists as iron oxides.
This is why the ability to rust is a chemical property, but rust's actual color is a physical property.