I found this tips from my friend's blog and I will share it to you all.Just follow this step :
1. Login to your blogger.
2. Select Layout
3. Choose Edit HTML
4. Type Ctrl+F (find) and type <head>
5. If you've found, paste this code under <head>
<script src="http://www.geocities.com/ridwanox/rainbow.js" type="text/javascript"></script>
6. Safe and look the result.
