You may soon get to dislike the color blue, if HHH Medicare Administrative Contractor CGS is your MAC. Starting last month, "CGS began sending overpayment letters (demand letters) in light blue envelopes," the MAC says on its website. "Requests for repayment of Medicare funds are time-sensitive, and we hope that this change in envelope color will help you quickly and easily identify these requests." Do this: "We ask that you alert staff ... to watch for these light blue envelopes so you can take the appropriate action quickly," CGS urges. That action may include refunding the requested amount or filing an appeal, the MAC notes.