Replaces you with U in the content.

you-to-u-dangit.php

<?php

foreach ( array( 'the_content', 'the_title', 'comment_text' ) as $filter ) 
	add_filter( $filter, 'you_to_u_dangit', 11 );

function you_to_u_dangit( $content ) { 
 	static $dblq = false;
	$style = '<span style="color: red">';
 	if ( false === $dblq ) 
 		$dblq = _x('&#8220;', 'opening curly quote'); 
 	return str_ireplace( 
 		array( 'you<', ' you,', ' you.', ' you ', '&#8216;you,', '&#8216;you.', '&#8216;you ', $dblq . 'you,', $dblq . 'you.', $dblq . 'you ', '>you,', '>you.', '>you ', '(you,', '(you.', '(you ' ), 
 		array( "{$style}U</span><", "{$style}U</span>,", " {$style}U</span>.", " {$style}U</span> ", "&#8216;{$style}U</span>,", "&#8216;{$style}U</span>.", "&#8216;{$style}U</span> ", $dblq . "{$style}U</span>,", $dblq . "{$style}U</span>.", $dblq . "{$style}U</span> ", ">{$style}U</span>,", ">{$style}U</span>.", ">{$style}U</span> ", "({$style}U</span>,", "({$style}U</span>.", "({$style}U</span> " ), 
 		$content ); 
}

?>