The vast majority of propellors on all ships are made of bronze as it stands up very well to electrolosis in water and is still easy to form.

Bronze propellors start out bright and shiny when new, looking much like a new penny. With age, the bronze turns darker and loses it's shine. It may get a slightly greenish tint in some of the corners, similar to the colour you see on copper roofed buildings but not as bright but only as a sort of transparent patina.

One detail that doesn't show up on most phots or models unless you know what to look for, is that there will be a zinc anode somewhere near the propellor, usually bolted around the shaft. This sacrificial anode is used to stop propellor and shaft from pitting due to electrical currents between the different types of metal.