<p>I need to change color of TextBox whenever its required field validator is fired on Clicking the Submit button</p>

Here's some self-contained HTML/JS that does the trick:
```
```
<html>
  <head>
    <script type="text/javascript">
      function mkclr(cntl,clr) {
        document.getElementById(cntl).style.backgroundColor = clr;
      };
    </script>
  </head>
  <body>
    <form>
      <input type="textbox" id="tb1"></input>
      <input type="submit" value="Go"
        onClick="javascript:mkclr('tb1','red');">
      </input>
    </form>
  </body>
</html>
```
```