Brian - all you need to do is right-click your "Reduction Target" under the Dimensions shelf, select Group, and add the members to the groups you want. Then just drag this group into your view and voila! If you want, you can also drag the original Reduction Target pill onto the Color shelf to see which members (and their quantities) make up the whole bar.
Thank Ben - I've done that before and I don't know why I didn't remember it. Thanks!