Here is your colored background, DaRk=BaN ...
This is the "base" code (expand from this as I did in the example above) ...
<textarea style="background-color : #6596BE;width : 300;height : 200" cols="" wrap="virtual">Text or any other content here</textarea>

Here is your transparent background, DaRk=BaN ...
This is the "base" code (expand from this as I did in the example above) ...
<textarea style="background-color : transparent;width : 300;height : 200" cols="" wrap="virtual">Text or any other content here</textarea>