March 2014 iOS iMovie update (red background, not blue) showing up on some student iPads and not others. What is going on?

On Thursday, March 6, 2014, I used iMovie with a group of third graders and half of the iPads had a new version of iMovie installed. It now has a red background. I went to see if I could update the app on the rest of the iPads and the update is not showing up. As you can imagine this proved rather challenging to have half of my students using a very different version of iMovie. Someone please help. iMovie has been a great tool in the classroom.