In the Lord of the Rings I recall some mention of when Cirdan gives Narya to Gandalf when the Istari arrive in Middle Earth. I think it is in the appendices but I cannot recall exactly, but I remember something about him suspecting Gandalf's origins and giving him the ring to aid in the fight against Sauron.
Throughout the novel, we learn that Saruman is more powerful than Gandalf and is his superior in some way. I recall somewhere in the novel Gandalf himself confirms this when he describes Saruman as the head of his order (here I assume that when he refers to "his order" he means the Istari - please correct me if this is wrong).
This being the case, I wonder if Tolkien ever discusses in interviews or other works the reasons that Cirdan chose Gandalf over Saruman as the person to pass Narya onto. It would seem to me that without the knowledge of the events to come that Saruman would be the more natural choice if Cirdan was intent on passing on Narya to someone else.