Hi,

I guess that you are referring to this sample - http://labs.infragistics.com/silverlight/lobsamples/2010.2/#/Samples/Grid/Styling/CustomHeaderFooter .

If you want to highlight the current page item you have to change the Selected state in PageItemStyle.

for example:
change this:
<VisualStateGroup x:Name="SelectionStates">
 <VisualState x:Name="Unselected" />
 <VisualState x:Name="Selected" />
</VisualStateGroup>

to:
<VisualStateGroup x:Name="SelectionStates">
 <VisualState x:Name="Unselected" />
 <VisualState x:Name="Selected">
  <Storyboard>
   <ObjectAnimationUsingKeyFrames Storyboard.TargetName="pagerItem"
             Storyboard.TargetProperty="Foreground">
    <DiscreteObjectKeyFrame KeyTime="0"
          Value="Red" />
   </ObjectAnimationUsingKeyFrames>
  </Storyboard>
 </VisualState>
</VisualStateGroup>

This will make the Foreground of the selected item Red.

To set the current page programmatically use the XamGrid.PagerSettings.CurrentPageIndex.

HTH