Using an AppCompat theme, the ProgressBar’s color will be the colorAccent you have defined.

To change the ProgressBar color without changing the accent color you can use theandroid:theme attribute overriding the accent color:

<ProgressBar  
    android:theme="@style/MyProgress"
    style="@style/Widget.AppCompat.ProgressBar" />

<!-- res/values/styles.xml -->
<style name="MyProgress" parent="Theme.AppCompat.Light">  
    <item name="colorAccent">@color/myColor</item>
</style>

To tint the ProgressBar you can use in the xml file the attributes android:indeterminateTintMode and android:indeterminateTint

<ProgressBar
    android:indeterminateTintMode="src_in"
    android:indeterminateTint="@color/my_color"
/>