There are a few ways to style alternating blog posts and a few ways to style more than two. This example does a simple count and gives 5 different styles to 5 different post containers that you can style. In this setup the only difference is styling the hover of the containing div to be different colors.

The Markup:

  
have_posts()) : $my_query->the_post(); $do_not_duplicate = $post->ID; ?>
  
 
	  
		

      
		
 
      
		
 
      
		
 
     
    

    
            
            
				

				
                
			
            

            
            
            
            
        

        

		

			
		

        

        
        
        

 
 

And the css:

.blog-entry, .blog-entry-2 , .blog-entry-3 , .blog-entry-4 {
	float: left;	
}
.blog-entry a, .blog-entry-2 a, .blog-entry-3 a, .blog-entry-4 a {
	width: 540px;
	float: left;
	display: block;	
	padding: 10px;
}
.blog-entry a:hover {background-color: #FAD827;}
.blog-entry-2 a:hover {background-color: #B79ECA;}
.blog-entry-3 a:hover {background-color: #B1D142;}
.blog-entry-4 a:hover {background-color: #7ACDD7;}
.blog-entry-right {
	width: 300px;
	float: left;
	margin-left: 10px;
	overflow: hidden;	
}
.blog-featured-image  {
	width: 200px;
	height: 200px;
	padding: 5px;
	background-color: #CCC;
	float: left;	
}