FLC OF AN MLG FAILED TO FOLLOW A SID DURING DEP RESULTING IN ATC INTERVENTION AND AN AMENDED CLRNC.

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WE WERE DEPARTING LAX FOR A MORNING ORIENTATION FLT TO LAS. THE FO; WITH WHOM I HAVE FLOWN QUITE A BIT; WAS OCCUPYING THE L SEAT; AS HE HAS COMPLETED UPGRADE AND WE ARE THEREFORE PERMITTED TO SWAP SEATS. OUR ASSIGNED SID; THE LOUPE 9 DEP; DEPARTS LAX ON A 250 DEG HDG. AT SOME POINT SOCAL DEP WILL ISSUE A L TURN DIRECT TO THE LAX VOR. ACFT ARE THEN EXPECTED TO REVERSE COURSE EXPEDITIOUSLY TOWARD THE VOR; XING IT AT OR ABOVE 10000 FT; AND DEPARTING ON THE 041 DEG RADIAL. AS I CAME BACK ONTO ATC FREQ AFTER HAVING CALLED BACK OUR TIMES TO COMPANY; IT APPEARED TO ME THAT WE WERE XING THE COASTLINE AROUND PACIFIC PALISADES; CONSIDERABLY S OF THE VOR. SHORTLY THEREAFTER; SOCAL DEP ASKED IF WE WERE TURNING TO JOIN THE SID; THEN ISSUED US A HDG TO 050 DEGS. AS IT TURNED OUT; THE FO WAS NAVING OFF THE #2 (FO'S) NEEDLE ON THE RMI DUE TO FORCE OF HABIT; RATHER THAN THE #1 (CAPT'S) WHICH HE SHOULD HAVE BEEN WATCHING WHILE FLYING FROM THE L SEAT. I HAD THE #2 NAV RADIO TUNED TO THE NEXT NAVAID AFTER LAX; AND IT REALLY WASN'T POINTING AT ANYTHING YET. I WAS SOMEWHAT FATIGUED DURING THIS OCCURRENCE DUE TO MY STARTING TO COME DOWN WITH A COLD; AND HAD RESULTANTLY HAD A POOR NIGHT'S SLEEP THE NIGHT BEFORE. FURTHERMORE; THIS GUY IS PRETTY SHARP (OR I WOULDN'T SWAP SEATS!) AND THE CHANCES OF HIM SCREWING UP A SIMPLE DEP ARE PRETTY SLIM. (OR SO I THOUGHT!) IN THE FUTURE; I WILL REFRAIN FROM SWAPPING UNLESS I'M FEELING PERFECTLY WELL; AND I'LL WATCH THE OTHER GUY LIKE A NEW HIRE ON HIS FIRST DAY!