To Set Up Display Overrides for Level Symbology

From the Symbology option menu, choose Overrides.
In the Level Manager dialog Level list, select the desired level or range of levels.
Adjust the symbology overrides using the controls built into the list for the selected level(s).
If Level Overrides is on in the View Attributes dialog (Drawing > View > Presentation > View Attributes), each changed level attribute (color, line weight, or line style) displays in place of the elements' own attributes.

Note: If Level Overrides is toggled on (Drawing > View > Presentation > View Attributes), elements display according to the override symbology. However, if override symbology is off for particular level attributes, the elements display per the element attributes. If Level Symbology is toggled off (Drawing > View > Presentation > View Attributes), the elements display according to the element attributes.