B767-300 Pilot reported a Cargo Fire B 6 and 8 amber light illuminated and the flight crew completed a diversion to an alternate airport.

Narrative

On Date; We were flying Aircraft X from ZZZZ to ZZZ and had a Cargo Fire 'B' 6 and 8 amber light illuminate. At the time I was sitting in the Captain seat; the First Officer was in his seat; and the Captain was taking a break. The First Officer and I noticed the issue on the center pedestal; but there was no EICAS indication. We ran the QRH for anything that would 'fit' the scenario; which was Cargo Fire 8.2. However; there was nothing in the QRH that fully matched the situation as there was no EICAS indication. After a brief search; we alerted the Captain to bring him into the loop. He went to the back and visually checked for a fire as well as smell for any smoke. He did not detect anything. After he came back we resumed our normal seats. We called Dispatch and was patched through to Maintenance. They also could not find anything that would fit the situation. We decided to patch the Director of Ops in on the situation; to try to get as many thoughts and suggestions as we could. The conclusion was made to go directly to our alternate ZZZZ1. We requested priority handling over HF asking the operator to patch the information through. As we came closer we got in touch with ZZZZ Control and fully brought them into the loop as to the emergency directly with us.Additionally; we knew we were going to land overweight; so we did our best to mitigate the issue; but ultimately we landed 6;000 lbs. overweight. It was written up in the logbook as well. We also discussed the issue of landing in [another country] with flight operations; and continued on as ZZZZ1 was our alternate; and dispatch informed Border Control. On approach we requested CFR to follow us and do a visual check after we landed. We were told on the radio; there was no indication of fire from their perspective. We parked; then they did a more thorough inspection; but ultimately we were told by crash fire rescue equipment there was no evidence of a fire.