Adjust line style, plus line weight, color and pattern.
Displacement set path style and display can be modified in the same way as other Revit projection lines. The line style is set on the Properties palette, and line weight, color and pattern display settings are modified on the Visibility/Graphics Override dialog for the view, or on the Object Styles dialog for the project.
Setting Displacement Path Style
(Modify) on the Select tab.
Setting Displacement Path Color and Line Weight for the View
Graphics panel 
(Visibility/Graphics).
Setting Displacement Path Color and Line Weight for the Project
Settings panel
(Object Styles).