This is a question that keeps getting asked and answered everyday. You'll find it in the Tutorials and FAQs in the upper right of the Zen home page.

View the source of your page from the browser.

Search for "Welcome".

<div id="taglineWrapper"><div id="tagline"><h1>Welcome</h1></div>

In the stylesheet.css look for id="tagline"

/includes/templates/your-template/css/stylesheet.css

Change the color associated with the object and save. Upload new to the server and refresh webpage to see your changes.

I'd use the sparkly background as a background and use solid black for the cart. All the sparkles make me want to look for a disco queen.