Coloring a Row in a NSTableView.

What I am looking to do is set the background color of the selected row in an NSTableView when a I button is clicked.
I've seen other cases where people have used tableView:willDisplayCell:forTableColumn:row: and setBackgroundColor: but I don't think that will work in my situation where I want it to happen when a button is clicked.

I know that I can find the selected row with NSTableView's selectedRow method and set the Background color for a cell with setBackgroundColor:.
Here's what I have tried :
- (void)tableView:(NSTableView *)aTableView 
  willDisplayCell:(id)aCell 
   forTableColumn:(NSTableColumn *)aTableColumn 
              row:(NSInteger)rowIndex {
    NSLog(@"Coloring Method Begun");
    int selectedRow = [outlineView selectedRow];
    if (selectedRow == nil) {
    }else {
        if (clicked == YES) {
            [aCell setBackgroundColor:[NSColor lightGrayColor]];
            clicked = NO;
            NSLog(@"Coloring Method Ended");
        }else {
        }
    }
}
    
- (IBAction)colorize:(id)sender{
    NSLog(@"Click Method Begun");
    clicked = YES;
    NSIndexSet *selectedRowSet = [outlineView selectedRowIndexes];
    NSIndexSet *selectedColumnSet = [outlineView selectedColumnIndexes];
    [outlineView reloadDataForRowIndexes:selectedRowSet columnIndexes:selectedColumnSet];
    NSLog(@"Click Method Ended");
}

But it seems that the delegate method is never triggered.