Continuity mistake: When Harry opens the letter from Sirius Black, he throws away the string that was tied around the letter. When it cuts, the string is back in his hand.
Continuity mistake: In the Triwizard champions' tent, Rita's photographer captures the moving photograph of Hermione and Harry hugging, and subsequently letting go of each other. Later, when Hermione reads from The Daily Prophet, just before Ron opens his package, in the close-up of the newspaper their hug, the release, and where they both stand are entirely different in the moving photograph. (00:54:50 - 01:05:20)
Continuity mistake: In the Great Hall, when Ron takes the dress robe out of the box, there is a plate beside Hermione which has two utensils on its left side and one utensil on its right. However, when Harry says, "It does match your eyes," and in another following shot, there is only one utensil on the plate's left side - the knife is now on the other side. (01:06:00)
Continuity mistake: When the students are dancing to The Weird Sisters at the Yule Ball, Viktor Krum can be seen at the back of the group, jumping up and down, with Crabbe/Goyle jumping up and down behind him with his hands on Krum's shoulders. Immediately after, however, Krum is seen dancing with Hermione, and Crabbe/Goyle has disappeared, with no time to move between shots. (01:16:20)
Continuity mistake: In the dorm, after Ron moans, "Yeah, that's me, Harry Potter's stupid friend" as Harry leaves his bed and walks to Ron, there is a single rectangular window beside his bed and another window about a foot above it. Later, after the Yule Ball, in the exterior zoom-in shot the crow flies toward the side-by-side double window, arched at the top, as it heads for the window sill, and in the next interior shot, the crow lands on the sill as Harry sleeps beside that window. (00:38:30 - 01:22:30)
Continuity mistake: When Dumbledore reveals the Triwizard Champions, in some shots one of the Weasley twins sits beside Harry and Seamus near the wall, along with Hermione, Ron, and Neville. In other following shots, both Fred and George are sitting together on the opposite side of the table.
Continuity mistake: There is a scene where Harry is holding the letter from Sirius and we can hear Sirius's voice reading the letter. The words on the letter are different from the words we hear Sirius reading. Particularly the end where Sirius says, "P.S. The bird bites" the letter says, "By the way, the bird bites."
Continuity mistake: When Rita grabs Harry to interview him, in the next shot, as the Quick-Quotes Quill springs up, the paint can, brushes, etc are on the steps. Their positions change in the Quill's first close-up, as it writes in the notebook. (00:39:55)
Continuity mistake: During the second task, just as Krum and Hermione pop up from underwater and Krum's sharkhead disappears, in this specific shot Fleur (NOT another Beauxbaton student) stands on the platform in the background and her hair is fairly dry, blowing a bit in the wind. However, in a following close-up, Fleur's hair is soaked and stringy.
Continuity mistake: In the dining hall, when Hermione begins reading Rita Skeeter's article mentioning the Hungarian bon-bon, the newspaper and Hermione's fingers change position between the semi close-up and close-up.
Continuity mistake: In the Great Hall, when Harry dribbles on himself, the plate to Hermione's right (as she holds The Daily Prophet up) has food and utensils lying on it. However, in the following shots, there is only an empty plate with utensils set on both sides, beside Hermione. (01:05:00)
Continuity mistake: In the cemetery, the gash on Harry's left cheek changes depending on camera angle, such as during Priori Incantatem when Cedric says, "Take my body back..." and then when Lily says, "Sweetheart, let go..." (02:04:30)
Continuity mistake: In the Great Hall, after Hermione quips, "Well spotted!" Ron imitates his brother (when he asked Angelina to the Yule Ball) by lifting up his arms to mimic dancing, and Snape promptly smacks the back of Ron's head. In the next shot, Ron holds a pencil in his formerly empty right hand. (01:11:15)
Continuity mistake: Towards the end of the Yule Ball, when Ron and Hermione walk to the staircase, seated on the stairs are two girls who are comforting a third girl in the center. When Hermione shouts, "Ron you spoiled everything," the girls' positions change between shots. (01:18:20)
Continuity mistake: After Fred and George drink the aging potion, when the twins jump over Dumbledore's Age Line, in this overhead shot Hermione sits at the edge of the long bench, with the closed book and crossed legs. Yet, in the next shot, as Fred and George begin congratulating each other, Hermione sits a few feet away from the edge, still with the closed book and crossed legs. (This is before she moves her seat and opens her book.) (00:29:00)
Continuity mistake: In the DADA class, whenever there is a shot facing the class room, we can see that Ron and Harry are in the middle of the class room and Parvati and Padma are on the viewer's right side of the room (screen). Yet, when Moody makes the spider float from Padma onto Ron's face, in the shot facing Ron, the spider floats onto his face from the viewer's left side of the room (screen) whereas it should have been the right side of the room (screen).
Continuity mistake: In class, when Moody shouts, "And hear across classrooms!" he throws the chalk at Seamus, and the way Seamus ducks over his desk noticeably differs between the two shots; he first leans down on his right arm, then on his left. (00:23:10)
Continuity mistake: At the Quidditch World Cup, when the kids reach the top, in the first shot facing them their positions are Cedric, Ron, Fred/George and Ginny. Just before the shot cuts, Ginny is just about to move behind a twin, and more to the point, three members of the Irish zoom by on their brooms between Ron and Cedric. In the next shot (from behind), as the Irish are still zooming by, now their positions are Fred/George, Ron and Ginny, with the Irish zooming by between Ron and Ginny. Between shots, Ginny has moved past three people and the zooming Irish on their brooms. Don't confuse the hat wearing twin for Ginny; her hat is green with a black buckle band and the twin's hat is green stripe. (Clearer on fullscreen DVD.)
Continuity mistake: After Harry overhears Snape and Karkaroff, when Snape confronts Harry and mentions the Gillyweed, the shelves behind the ladder in the store room are quite visible. Once Snape finds the bottle of Veritaserum things behind the ladder differ.
Continuity mistake: When Harry is attacked by a multitude of Grindylows he sustains numerous injuries, particularly the one on his jaw and neck. The position and characteristics of that wound repeatedly change in the following shots.
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.