How To: Set a single feature's symbology to be different than the rest of the layer
The instructions provided below describe how to set a single feature's symbology to be different than the rest of the layer. For example, you may have symbolized a polygon layer to be a single color but you would like to quickly set a particular feature to have a different symbol than the rest of the layer.
Follow the steps below.
Right click the layer then click layer properties > symbology > categories > unique values > value field.
Change "value field" to the field that identifies the feature you want to change the symbology for.
Click add values and select the feature from the list then Click OK.
Change the symbol properties by clicking the symbol.
Repeat steps 3 and 4 for as many features as you like. If you have many features you would like to change the symbology for, consider using a different renderer that will symbolize automatically.