FO OF AN LGT FAILED TO TURN AND FOLLOW SID ON INITIAL CLB AFTER TKOF SINCE HE WAS REFERRING TO THE WRONG SID DEP.

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DURING PREFLT I BRIEFED THE RIVER 6 DEP FOR RWY 10L AND I LOADED THE PDX 085 DEG RADIAL OUT TO ABOUT 40 MI FOR MY FO TO FLY. WE WERE CLRED TO TAXI TO AND HOLD SHORT OF RWY 10L. AS I WAS CONSIDERING STOPPING AND ASKING TWR; I HEARD TWR CLR US FOR TKOF. AFTER GEAR UP; I ASKED MY FO IF HE WANTED LNAV (TO TRACK THE PDX 085 DEG RADIAL). HE SAID; 'NO HDG SELECT.' I THEN ASKED IF HE WANTED 085 DEG HDG; AND HE SAID NO; 'SHE (TWR CTLR) SAID FLY RWY HDG.' I LOOKED AGAIN AT THE DEP AND SAW THAT IT ALLOWED EITHER 085 DEG RADIAL OR 'AS ASSIGNED.' SINCE HE SAID THIS WITH GREAT CONFIDENCE; AND TWR WAS NOW BUSY WITH OTHER FLTS; I DIDN'T QUESTION IT. UPON CONTACT WITH DEP CTL; WE WERE GIVEN A L VECTOR TO 080 DEGS AND TOLD IT WAS FOR NOISE ABATEMENT DOWN THE RIVER. JUST ABOUT THEN MY FO SAYS; 'OH; I WAS LOOKING AT THE WRONG DEP.' HE HAD THE PORTLAND 5 DEP OUT (THE BACK OF THE RIVER 6) WHICH IS A RADAR VECTOR DEP. THIS WAS ONLY THE BEGINNING OF THE SECOND LEG WITH THIS FO. SUBSEQUENT EVENTS HAVE LED ME TO BELIEVE THAT TWR PROBABLY DID NOT CLR US TO MAINTAIN RWY HDG. I KNEW THAT I COULD EASILY HAVE MISSED HEARING THE RWY HDG CALL DURING THE TKOF CLRNC BECAUSE I WAS DISTR BY THE ACR Y JET; BUT I DON'T THINK SO NOW.