Laura, what you are seeing is the rough cut back of the stones that make up the stairs. The are painted white. This light was built back in 1811, many of the lights from this time had stone or wood steps originally. Amelia Island in Florida is another light with stone steps. (Lighthouse friends photo don't have access to mine it's at home)
Below is the Lighthouse friends page on the light, about halfway down in the history of the light is a link to another picture of the stairs.
