When I try to send a fax, I see the message Fax not sent. Resend using the Start B&W button. Why?

• You sent a fax using the  Start Color button to a fax machine that prints only in black and white. Send the fax again, but press the  Start B&W button.
  
  You can also select to send faxes only in black and white. See Selecting Fax Settings for details.