The Preferences dialog box's Highlighting category controls the highlight color when various elements are displayed in the Design pane. Table 18-2 lists the default colors.
Option
Default
Controls the border of:
Editable Regions
#CCFFFF (light blue)
Editable regions of a template-based document
Locked Regions
#FFFFCC (light yellow)
Noneditable regions of a template-based document
Library Items
Instances of library items
Third-Party Tags
Elements added by third-party tags