My guess is she changed shoes. The heels on the teal shoes are much higher, so not as conducive to walking much. While, when she is going in an in the "parade" after she is in the tan shoes.

The changing shots of the podium with kids showing up in some shots but not the others is more telling than this because there is a gap of time between going into the Capitol and going on the podium when she could have changed her shoes.

So, it could be a snafu (Hollywood has these all the time) or it could be that she simply changed her shoes.