highlighting polygon boarders

[CrystallSalmon]

I'm trying to change the boarder to highlight a specific polygon in a layer. When I change the boarder (from solid line to gradient) to highlight that specific polygon, part of the boarder is blocked by the adjacent polygon. How do I fix this so that I can view the full boarder change. 

[LindaWilliams1]

You can use a negative offset in your border outline symbol to move all the borders slightly within their polygons so that they don't overlap.