That's a cool way to put it, but it's not exactly rust like on a bike... it's iron oxide in the rock itself. The red color is basically the same stuff, just formed over millions of years. The park ranger was probably trying to make it simple for people to picture. It's still a neat way to think about it though.
Not exactly rust like on a bike" - alright, calm down, it's basically the same science, just slower. Some people act like it's a crime to keep things simple. As long as it gets the point across, who cares if it's not perfectly accurate?