How to add an outline to a quad

I am trying to create a nice looking outline to these board pieces that get rotated constantly. So I thought "why not just put another quad in front and have that the color of the outline." So I tried it and when the object was rotated a bunch of dark lines appeared and it just looked plain nasty. I need to be able to change the color of the piece but I don't need to change the color of the outline. Are their any ideas on how to do this? I thought that maybe shaders could do this but I have absolutely NO knowledge on shader languages. This feels like a simple task but I can't seem to get it right.

Thanks in advance!