You can edit object styles on the map by adding new styles and removing existing styles, which may affect what the styles look like in the legend. A legend does not update automatically except when overriding, changing, or removing an existing style. For other style changes made to a layer, you must refresh that layer's legend frame.
You cannot refresh a thematic legend frame. Legends based on raster layers are automatically refreshed when changes are made to the raster table. When thematic layer properties are changed the thematic legend refreshes automatically.
To refresh the contents of a legend frame after making style changes to a layer:
Right-click on the legend frame and click Refresh Legend Styles.
The legend frame refreshes to show the most current styles in use for the layer.