Trying to Change the Look of a Zone

First off, KUDOS on this module!

I am trying to theme the zones without success. There is another post regarding this where it is stated:

If you want to customise composite layout themeing, you can start by overriding the CSS styles in .../composite/composite.css or .../composite/theme/*.css, but you should override that in your own Drupal theme. Don't modify the composite css files.

And then if you need more control, you can override the .tpl.php files in .../composite/theme/*.tpl.php. Again, this overriding is done in your Drupal theme. Don't modify the files in composite.module itself.

I had modified the CSS in the composite module CSS file directly, but un-modified it when I read this. It didn't make any change anyway, even with clearing cache.

Then I did as instructed and overrode the CSS by copying the CSS from the module and putting it into my theme's (Garland) CSS.

.composite-threecol-33-33-33 .composite-column-middle .composite-zone-inner {
  margin: 0 .33em 1em .33em;
  border: 1px double black;
  color: black;
}

The border and color were the only additions I made, but this again caused no change to the page's appearance. (Cleared cache again)
I then added the above CSS to composite/composite.css and again had no change.

Basically, no matter what I do, no change shows up on the page.

Can you tell me how to make CSS changes that affect the appearance of a given zone in Composite Layout?

Many thanks!