To keep your users aware of the fact that there's asynchronous
actions in progress, the indeterminate progress bar is a common
practice. One thing I've noticed is that when you add a ProgressBar
element to a page in your Windows 8 page, the color of the
indeterminate state is static meaning that there's no public
property that you can use to set a specific color. One approach
might be to retemplate the entire control, but it's a bit drastic
when there's actually an easier approach.