In this photo of a sketch by courtroom artist Janet Hamlin and reviewed by the US Department of Defense, Khalid Sheikh Mohammed holds up a piece of paper during a court recess at his Military Commissions pretrial hearing.

Guantanamo Bay Naval Base, Cuba - The Pentagon has given a partial explanation to a Guantanamo mystery: How the self-proclaimed mastermind of the September 11 attacks managed to dye his beard.

Khalid Sheikh Mohammed's bushy grey beard has been colored a rusty orange during court appearances. Spectators had assumed he used henna, which is used by some Muslims as a hair dye.

A Pentagon spokesman says Mohammed used “natural means,” such as juice from berries that he receives in his meals. Army Lt. Col. Todd Breasseale said Tuesday that Mohammed did not receive any “outside” means to color his beard.

Mohammed is kept under such heavy security that his lawyers can't even reveal routine conversations with their client.

He is charged with four other prisoners with aiding and planning the September 11, 2001, terrorist attacks. - Sapa-AP