Step 1: Open the Task Pane from the button on the Office Timeline ribbon
With the Task Pane open, click any object on your slide to surface the custom controls for that particular object.
Any customizations you make will make will only be applied to that object.
Step 2: Formatting Milestones
Click on a Milestone marker to change is shape, size and color. From here you can also format your milestones font, date, and the color of its connector.
Step 3: Adding style preferences to your tasks
Click on any Task to customize the shape, size, and spacing. You can also You can also access the Percent Complete and Task Duration controls for here.
See these quick videos for more tips: