People seem to think a root canal leaves a lifeless tooth. if that is true, will the tooth turn black?

Not always: Just because a root canal was done, doesn't always mean a tooth will darken. But, it is fairly common over time. And by time i mean months to years. To protect the tooth and not show it dark..A crown can be placed. But it is not always required to crown a root canaled tooth. The tooth is lifeless, it just has no nerve, but it can still decay and must be cared for just as you do the others.

Not often: A root canal treatment fills the chamber where the nerve is normally found in a tooth, so technically it is a lifeless tooth. Many factors can cause a lifeless tooth to discolor, root canal treated or not. However, should the tooth darken it can be bleached and usually matched to the other teeth. Typically once a root canal is finished the tooth will not darken very much, if at all.