Primary Sidebar – formatting with colored box and different text color

Hi Actually I manually entered a html formatted text to appear as a box on the primary sidebar. --> see formatting here: <div style="background:#4f524f;color:#ffffff;border:1px solid #ccc;padding:10px 10px;"> Is there a way to customize CSS in such a way, that primary sidebar is independent from its content formatted with a colored box and different text color? I want to automize sidebar content by placing latest post there in a different format. Thanks for your support Best regards Stefan