Thank you for posting this question! In this short article, I will help you out on how you can change the color of the 'Follow us button' inside your widget.
In order to make the changes you will need to:
1. Navigate to the 'Widgets' tab and open the desired widget. Once you have opened the editor, click on the 'Header' settings:
2. Now you can select the color of the button the color of the hover state(color once you hover over the button with the mouse), and the text color of the button: