No, on the same page, just link in the print style sheet. The media specifies what it controls. media="screen" says to display this css on the screen and media="print" says to use this css when printing. Like so:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<title>Blah</title>
<meta http-equiv="Content-Type" content="application/xhtml+xml; charset=iso-8859-1" />
<meta http-equiv="content-script-type" content="text/javascript" />
<meta http-equiv="content-style-type" content="text/css" />
[b] <link rel="stylesheet" type="text/css" media="screen" href="/styles/blue.css" title="Blue" />
<link rel="stylesheet" type="text/css" media="print" href="/styles/print.css" />[/b]
</head>
<body>