My nrwborn has ring around anus?

Anal fissures. I believe you are referring to anal fissures. I see a lot of newborns with it. They look like tears around the anus/rectum.May cause bleeding when constipated or you may see blood streaks in the stools.Usually benign.
Different skn color? There is often a different tonal quality of the skin around the outlet varying in redness or pinkness as you go from internal to outside skin.If there is another zone of increasing redness as u go out further, it is often due to irritation by acidic stool or germs. The outer rim of the outlet can appear like a drawn purse string creating a transient ring effect. If irritated, a look see is worth it.