Gosh, we do take in every detail don't we? I wear contacts myself. I personally don't have trouble with mine popping out but I wear rigid gas permeable lenses, not your traditional soft floppy contact lenses. I have heard they do that, maybe the technology has come further along by now that they don't. I would certainly hope that if contacts are touted as perfect for an active lifestyle, etc, they don't just fall out of your eye for something such as an actor's battle scene. What I have noticed with my lenses is that my eyes are MUCH more sensitive both to light and any speck of anything that gets in my eye...and maybe if Bloom was kicking up some dust in a battle scene, he left them out. It really hurts to get stuff in your eyes with them in, a LOT worse than when your eyes are "nude".
So by this discussion, I'm assuming that Orlando Bloom either wears colored contacts in real life or needed them as costuming to change his eye color to Legolas'.
As long as we are talking about eye color, I wonder if anyone noticed Gollum's eyes in the movie. I hadn't gotten to the part where Tolkien says that Gollum's and Smeagol's eyes change from blue to green, not sure who has which. At any rate, I didn't know about it either time that I saw the movie so I wasn't watching for it. Did anyone notice if Gollum's eyes change when he switches to Smeagol?