Appearance Settings - Legend
Every event you add to a timeline gets a color. You can keep that default or change it to something that carries meaning. On a project timeline, for example, you might give completed events one color and events that are delayed or at risk another, like yellow or red.
To help viewers understand what each color means, you can add a legend to your timeline.
Add a Legend
To add a legend, follow these steps:
Click the Appearance button.
Select Legend.
Add a description for one or more of the colors.

Check the Display legend option. The legend then appears on the screen and in certain exports.

Click Save Changes.
Remove a Legend
Click the Appearance button.
Select Legend.
Delete the descriptions you added for the event colors.
Uncheck the Display legend option.
Click Save Changes.

