Revealing mistake: A giant lizard is stepped on by Boone. The lizard's skin turns red after being stepped on. It becomes so red that a nearby rock begins reflecting the red light. (01:55:40)
Continuity mistake: Judah Ben-Hur removes the large ring he had received from Arrius and gives it to Pontius Pilate to return to Arrius. Following this, he returns to the leper colony with Esther, and he reunites with Miriam. When Judah is told Tirzah is dying, as Judah searches the cave for Tirzah, he is once again wearing the large ring he had received from Arrius, on his right index finger. Then, that ring vanishes when he finds Tirzah.
Suggested correction: Ben Hur got the ring from Arrius, not from the Emperor. When he goes to the leper colony the first time he is still wearing the ring. Later he gives the ring to Pontius Pilate to return it to Arrius. Then, when he goes to the leper colony the second time he is not wearing the ring anymore.
Aside from changing the mistake's wording to Arrius, the mistake is indeed correct. Rewatch the scenes. Judah Ben-Hur takes off the large ring he had received from Arrius and gives it to Pontius Pilate to return to Arrius. After that scene, he meets with Esther, and they both return to the leper colony. Judah speaks with Miriam, his mother, and he's told Tirzah is dying. Then, as Judah begins to search the cave for Tirzah, Judah is now wearing the large ring he had received from Arrius, on his right index finger. That ring vanishes when he finds Tirzah. The mistake is quite valid.
Continuity mistake: When Merryweather makes the dress blue a second time, it starts off on a ribbon that wraps itself around the dress waistline. The ribbon doesn't make it onto the completed dress.
Suggested correction: Hardly a mistake, since they're using magic and the dress changes multiple times.