I get this question more than any other question. And as there is no real right or wrong answer for this question I hold firmly to the stance of "keep it simple."
Now as a commercial photographer my default on any question is keep it simple. So it should be no surprise that I feel the same way with your outfit for your headshot. Choosing a simple solid-color tops for your headshot will keep the image clean and the focus on your face. We want the viewer to connect primarily with your eyes not some busy pattern or bright color of your shirt.
Now I don't feel you need to have a bland outfit on for headshots, you can layer and what not to create some texture but we don't want it overbearing.