B757-200 CREW EXITED RWY AND CROSSED A GREEN PAINTED; NON LOAD BEARING AREA; AT ORD.

Narrative

DURING LNDG ROLLOUT ON RWY 4R; ORD; WE EXITED RWY AT TXWY Q. THIS IS A HIGH SPD TXWY WHICH IS JUST BEFORE THE END OF RWY 4R. AS WE CLRED THE RWY; I NOTICED THE SURFACE WAS PAINTED GREEN AT THE POINT WHERE THE TXWY Q INTERSECTS WITH THE EXTENDED CTRLINE OF RWY 9R. I THEN REALIZED SOMETHING WAS SPECIAL ABOUT THIS EXIT; BUT IT WAS TOO LATE TO CHANGE EXITS. WE CONTINUED TO CLR TXWY Q ONTO THE PAD AREA AT THE END OF RWY 4R AND RWY 9R. WE CALLED GND CTL AND THEY SAID TO TAXI TO THE GATE. NOTHING WAS SAID ABOUT TXWY Q. AT THE GATE I THEN READ A NOTE ON THE ARPT DIAGRAM PAGE WHICH SAID; 'DO NOT USE TXWY Q UNLESS TOLD TO DO SO.' I LOOKED FOR A COPY OF THE ARR ATIS BUT REALIZED WE DID NOT PRINT IT (WE HAVE ACARS). THE NEW ATIS NOW SHOWED DEPS ON RWY 9R AND THE STATEMENT 'DO NOT USE TXWY Q UNLESS TOLD TO DO SO.' THIS GREEN AREA ON TXWY Q MUST BE PART OF THE CLEARWAY FOR TKOFS ON RWY 9R; BUT DO NOT REMEMBER IF RWY 9R WAS BEING USED FOR TKOF DURING OUR ARR. CONTRIBUTING FACTORS INCLUDE NOT READING ARR ATIS THOROUGHLY DUE TO ITS LENGTHY CONTENT.