Continuity mistake: In the scene after the old caretaker is killed, Ron is seen sleeping on the bed and as Hermione is about to wake him up his arms change position. His right hand is first resting on the pillow, when it cuts it's under the pillow. (00:03:55)
Continuity mistake: When we first see Hermione, she puts the candle down on a chest of drawers or something similar. In the next shot it has moved to the edge of the chest of drawers. (00:03:45)
Revealing mistake: During the Yule Ball there is a shot of Professor Moody sitting on a bench tapping time with the music. One can easily see a green object beneath the bench. It is apparent that a hole was cut in the cushion with his real leg hanging below the bench covered with a green leg and foot sleeve. The large green object is his foot with a red dot on his toe. In post production the actor's real leg and foot is to be removed digitally via green screen-like technology and replaced with a digitized artificial one. The red dots are to help coordinate the movements and position of the artificial leg with the actor's real one. This shot obviously got missed by the postproduction team. If you look closely you can also just make out his knee peeking below the fringe of the bench. (01:18:50)
Continuity mistake: When Dumbledore rages on Harry and asks him if he put his name in the Goblet of Fire, he first only put his right hand on Harry's shoulder, but in the next shot his left hand also appears on the other shoulder.
Answer: Not at all. In fact, David Heyman made the decision for his eyes to be blue in the films for him to be more scary! They felt that his red eyes in Sorcerer's Stone did not show enough emotion to make him an evil character. It was felt in Goblet of Fire that the light blue eyes would be perfect to show his evil in the moonlight, and they kept it on for later films.