I thought i had already posted this earlier this month but i guess i forgot sorry.  For those of  you that do not want to use the standard plane jane white or whatever color new message popup window here is how to change it.   Took me alittle bit of time to find it because its in static dir which i did not expect.  

You need to edit  ow_static/plugins/base/css/ow_css

This will do most of the job however there are a couple of items in the normal theme css you might need to change such as textarea and input items, but those are easy to find.

Here are the before and after images, and here is the file attached if  you want to see how i did mine.  Mine is not finished yet i am playing with colors still but youll get the idea. 

and then in your base css for your theme change this 1 item background value and it will take care of that white background left over.. 

.ow_chat_dialog {

display:none;

width:251px;

margin-left:8px;

font-size:11px;

background-color:#872626;  /* was background-f1f1f1; */

border:1px solid #ccc;

-moz-border-radius:3px;

-webkit-border-radius: 3px;

-khtml-border-radius:3px;

border-radius:3px;

-webkit-box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);

-moz-box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);

box-shadow:0 2px 4px rgba(0, 0, 0, 0.2);

vertical-align: text-bottom;position:relative;

}

done, 

happy coding

dave

icodemods.com