Request: Add support for plain text content

I am trying to add a quick note wherein I have given an inline style code so they can paste it in certain posts if needed but the editor strips all kinds of html code.

Example I was trying to show this in the quick note so they can just copy and paste this:

Just change the color codes to any color code you want.
<style>#content-area {background:#000000; color:#ffffff;}</style>

But after saving this becomes:

Just change the color codes to any color code you want.
#content-area {background:#000000; color:#ffffff;}

Can you implement a plain text mode wherein anything we enter will be shown as is?

http://wordpress.org/plugins/client-documentation/