You can override the representation color and symbology for selected features, or make them follow a different representation rule.

To do so, add the Representation toolbar and the Editor toolbar if they are not already present. Make the layer you want to edit (in this example, WetlandsA_Rep) the only selectable layer, and start editing.

Next, using the Select tool on the Representation toolbar, select the feature (in this example it is a swamp polygon). A rectangular selection box appears around it.

Open the Representation Properties dialog box to examine the selected feature. You can now create an override of the background color of the swamp.

Click the Color box below Solid color pattern. Choose a green color patch.

The color of the selected swamp feature changes, and a paintbrush icon appears to the right of the Color box to indicate that this property has an override. All other swamps in the map still follow the original rule, but this particular swamp has a color override. All other properties of the rule are still followed.

To remove the override, click the paintbrush icon. The override is removed, the paintbrush disappears, and the background color of the swamp returns to blue.

You can also assign the selected feature a new representation rule. With the swamp still selected, choose the Bog representation rule from the drop-down list. The feature representation now follows the representation rule for a bog and is symbolized accordingly. Click the Representation rule drop-down arrow again and choose Swamp to return the symbol to the original rule.