I’ve uploaded a new code sample! This sample explains how to create Windows Forms Applications with non standard borders. Think rounded corners. You can view this code sample here
Rounded Corners Form
New Code Sample – Non Standard Windows Forms Borders
Published January 12, 2013 Code Samples , New Version , Opensource 1 CommentTags: Form Borders, NonStandardFormBorders, TransparencyKey, Windows Forms
Software by Default 
I guess you can’t set the color of the standard border of a button in Windows Forms.