The flashing highlight makes selected items easier to see in the Acrobat window when many items are selected.

To find a selected item:

The selected item or items flash with the highlight color you specified in the Adobe Acrobat Preferences menu.
Tip: Using this flashing highlight feature is also helpful for highlighting a group of items that have the same characteristics, to check which of the selected items the Apply button in the Properties Editor will affect.

 

See Also

Setting selection colors