pozadina na paragrafi

<!DOCTYPEhtml>
<html>
<head>
  <meta charset=utf-8/>
  <title>Title</title>
</head>
<body>
<input type="button" value="Click to set paragraph backgorund color" onclick ="background ()">
<p>Paragraph 1</p>
<p>Paragraph 2</p>
</body>
</html>

<script>
  function background() {
    docBody =document.getElementsByTagName("body")[0];
    myBodyElements = docBody.getElementsByTagName("p");
    myp1=myBodyElements[0];
    myp1.style.background ="rgb(255,0,0)";
    myp2 = myBodyElements[1];
    myp2.style.background = "rgb(255,255,0)";

  }
</script>