I opened up the color head again to see where it could have come from. I'm pretty sure it's from the lever that toggles the ND filter (i.e. swings it in and out of the way).

TPPhotog, is it possible for you to get a photograph of your color head so that I can use that as a reference? I'm looking at the lever nearest the ND dial. There should be a piece that is moved by the lever to push the arm that controls the ND dial out of the way.