I digged into the code and found how to change the border.
You'll need to download the xml file and find this line (1323) with Notepad or Notepad++ :
Code:
<div id="vsapp_boxswitch" style="padding:0px;margin:0px;border:1px solid {vb:stylevar shade_color};border-top:0px;{vb:raw vbcollapse.collapseobj_vsapp_boxswitch}">
Take out
Code:
{vb:stylevar shade_color}
and replace it with your color of choice.
I did the following for a black border.
Code:
<div id="vsapp_boxswitch" style="padding:0px;margin:0px;border:1px solid #000;border-top:0px;{vb:raw vbcollapse.collapseobj_vsapp_boxswitch}">
and this was the result:
Once you have edited and saved, go to the plugin manager, add new, allow overwrite and enjoy