Annotation allows you to draw straight line, freeform line, highlight transparent line, and shape on your slide presentation.
Annotation
Shape
How-to :
To change the color of the line and shape
Click and select the color in the color palette around the toolbox.
To delete line and shape
click to delete one object at a time or to delete all the annotations.
Annotation Annotation
To change the color of the line and shape
to delete one object at a time or 
to delete all the annotations.