Corrected entry: At the end of the story the Grinch has blue eyes except for one shot - when he becomes shocked seeing the sled full of Christmas things begin to slide off the mountain - where they're momentarily red again.
Corrected entry: The Grinch has red eyes until he has a change of heart. Then they turn blue and remain that way for the rest of the story.
Correction: This isn't trivia, but one of the main plot points showing the Grinch's change of heart.
Corrected entry: At the beginning the Grinch is looking down on Whoville and drumming all his fingers. But when it cuts to another angle, he's suddenly only tapping one of them.
Correction: It doesn't take a minute to go from drumming all fingers to just tapping one of them. They wouldn't need to change scenes for that.
The Grinch is tapping all of his fingers as he looks down at Whoville; then, immediately in the next shot, he's just tapping his index finger. It might not take long for someone to go from tapping all their fingers to just one of them, but we don't see the Grinch adjusting his fingers at all between shots; he just goes from tapping all his fingers to just one finger instantly. I'd say this is a valid mistake.
Correction: This is not a mistake, it is done deliberately. It could be because of the stress/shock of losing the sleigh.