Continuity mistake: When the Grinch has his change of heart, his eyes change from red to blue. However, when he looks up and sees that the sled is about to fall, his eyes are red again. When he's running uphill, they're back to blue.
Suggested correction: His eyes turned red again because he was afraid that the sleigh would fall. After he finds the strength to pull the sleigh back up, his eyes turn blue again.
While it's true his eyes go back to red when he sees the sleigh about to fall, when he's running after it, they're back to blue. They switch back and forth. And you can tell they're suppose to be blue because the part around it is white (the sclera if you will) instead of yellow.
I still think it's a creative choice showing his determination. When he sees the sleigh about to fall, his eyes turn red, they turn blue again when grabs Max, turn red again when the rope holding Max breaks, turn back to blue as he races after it, turn back to red when he realises it's too heavy, and finally go back to blue and stay that way when he finds the strength to pull it up. It's pretty consistent with his emotions in each shot. His eyes are only red during the parts where he isn't determined (and during the parts earlier when he's evil).
