Show multiple milestones on a summary bar

I want to be able be able to have multiple milestones summarized on a roll-up summary bar. Additionally, each symbol will be a different color.

To specify that a milestone should be shown on a summary bar:

Using the arrow tool, click the milestone.
On the toolbar (Current Object: Symbol), choose the Summary tab)
Select Include this symbol on this Summary Bar level. To the right of this option, a level choice can be made. (Or, choose the option above).