CL600 CREW TURNS THE WRONG WAY WHEN THEY RECEIVE A NON STANDARD TERMINOLOGY HDG CHANGE AND BECOME DISTR WITH FMS.

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LEVEL AT FL390; GIVEN HDG CHANGE FOR TFC OPPOSITE DIRECTION MILES AHEAD (15 DEGS TO THE R). I READ BACK 15 DEGS TO THE R AND LOOKED DOWN FOR A MIN TO FINISH PROGRAMMING FMS FLT PLAN. WHEN I LOOKED BACK UP WE WERE LEVEL; DIDN'T NOTICE CAPT HAD TURNED OPPOSITE TO INSTRUCTIONS. SINCE HDG CHANGE WASN'T BIG; DIDN'T NOTICE BANK OPPOSITE. THEN ATC ASKED WHAT OUR HDG WAS AND WHEN I XCHKED MY BUG WITH WHAT WE WERE ON; SAW MISTAKE AND TOLD ATC WE MESSED UP. WE GOT A DSCNT CLRNC TO MAKE HIS PLANNING (ATC) WORK OUT AND WERE TOLD TO DO A GOOD RATE DOWN. (NO VISUAL OR TCASII TA'S.) CAPT DIDN'T KNOW WHY HE TURNED THE OTHER WAY; JUST A BRAIN BLOCK. I FLY WITH THIS PERSON ALL THE TIME AND HE'S A VERY EXPERIENCED SENIOR CAPT. JUST DIDN'T CATCH THE TURN. WE SHOULD PROBABLY NOT LOOK AT FMS UNTIL CORRECT TURNS/OTHER CHANGES ARE COMPLETE. THERE IS A LOT OF BUTTON PUSHING AND STAYING AHEAD OF ELECTRONICS IN THESE MODERN JETS. IN ADDITION; CTLR INITIAL INSTRUCTIONS WERE GIVEN AS 'LET'S SEE; 15 DEGS TO THE R' WHICH CAPT THOUGHT HE SAID 15 DEGS L; EVEN AS I READ BACK 15 DEGS TO THE R. IT WAS A LITTLE CASUAL IN THE WORDING FOR AN ATC INSTRUCTIONS.