The reason why the bar is of that color is because of the style you have selected. That is a fixed style and uses the system themes for the generation of UI elements.
Look at the source code from here. This progressBarStyleSmall attribute uses the styles defined here.
<style name="Widget.ProgressBar.Small">
<item name="android:indeterminateDrawable">@android:drawable/progress_small_white</item>
<item name="android:minWidth">16dip</item>
<item name="android:maxWidth">16dip</item>
<item name="android:minHeight">16dip</item>
<item name="android:maxHeight">16dip</item>
</style>
Just create a custom style following the example from the android source code. You would need to replace the android:indeterminateDrawable to what you want.