Apply no color to outline in symbology - Esri Community

Limited options in 'Format All Symbols' - Esri Community

ArcGIS Pro : Apply Color scheme on selected symbol - Esri Community

Cartographic Styles

arcmap - Quickly changing outline color of polygon in ArcGIS

Symbol Styler: Using complex symbols in Map Viewer

Symbolise by outline in ArcGIS Pro - Exprodat

Symbolize map layers—ArcGIS Pro

Cartographical Symbol Construction with MapServer — MapServer 8.0

Add Transparency Option to Format All Symbols - Esri Community

How To: Blur the Boundary of Polygons in ArcGIS Pro

Design symbology for a thematic map in ArcGIS Pro