FLC ON VISUAL APCH ARE DISTRACTED FROM THE RWY VASI GS LIGHTS BY RED RWY BOUNDARY OBSTRUCTION LIGHTS.

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LGA APCH KEPT US AT 3500 FT OVER HUDSON RIVER AND CLRED US FOR VISUAL TO RWY 13. DUE TO RWY 4/22 CLOSED. TUNED ILS TO FIND GS 2 DOTS BELOW US; BUT WE WERE CONFUSED AS VASI LIGHTS APPEARED OK -- RED OVER WHIET. I CONTINUED TO COMPLAINED TO FO THAT WE HAD TO BE TOO HIGH; BUT HE; TOO; SAID 'VASI SHOWS OK.' ABOUT 2 MI OUT; I DETERMINED THAT UPWIND 'WHITE' VASI LIGHT WAS NOT VISIBLE DUE TO PLACEMENT OF RED OBSTRUCTION LIGHTS ON GND AT LGA WHICH OUTLINE RWY LIMITS AT NIGHT TO KEEP ACFT AWAY FROM WATER'S EDGE. I WAS SEEING INSTEAD OF WHITE UPWIND VASI LIGHT; A NEARBY RED OBSTRUCTION LIGHT AND MISINTERPRETING THE 'RED OVER WHITE' AS ON GLIDE PATH SIGNAL. WHICH IT DEFINITELY WAS NOT. IF CONTINUED ON SAME FALSE GLIDE PATH (VISUAL) WOULD HAVE OVERSHOT. SUGGEST (A NOTIFIED LGA ARPT OPS) THEY REMOVE (OR SHIELD) RED OBSTRUCTION LIGHTS IN VICINITY OF UPWIND VASI LIGHT. TO MAKE THAT LIGHT CLRLY VISIBLE AND EASILY IDENTIFIABLE. NOTE: VISUAL APCHS TO RWY 13 ARE VERY RARE AS IT'S MOSTLY USE FOR IFR. THIS SIT -- NIGHT VISUAL TO RWY 13 -- IS RATHER RARE AND I SUSPECT THIS HAZARD HAS EXISTED; UNNOTICED; FOR YRS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT SHE WAS TURNED ONTO A HIGH SHORT FINAL (3500 FT) FOR A VISUAL APCH AND IMMEDIATELY LOOKED FOR THE VASI LIGHTS. SHE EXPECTED TO SEE 'WHITE OVER WHITE' SINCE THE ACFT WAS WELL ABOVE THE GS. HOWEVER; THERE APPEARED RED OVER WHITE WHICH IS THE REVERSE OF THE RED AND WHITE POS BUT THE RED LOOKED LIKE A VASI LIGHT SINCE IT WAS DIRECTLY IN LINE WITH THE WHITE VASI LIGHT LOCATION. WHEN THE ACFT DSNDED DOWN TO THE ACTUAL ILS GS ALT; BOTH VASI LIGHTS WERE OBSERVED. HER CONCERN IS THAT THE RED OBSTRUCTION LIGHT IN LINE BE SHIELDED FROM THE APCH END OF RWY 13 OR MORE ADDED IN A RADIUS FROM THE VASI TO PRECLUDE ANY MISTAKE. SHE FURTHER MENTIONED AGAIN THAT THIS RWY IS SELDOM USED FOR VISUAL APCHS AND WAS BEING USED AS SUCH BECAUSE OF RWY 4 BEING CLOSED. SHE STATED THAT BOTH CREW MEMBERS OBSERVED THE SAME VASI INDICATION AND THAT THERE WAS NO NOTICEABLE DIFFERENCE IN THE SHAPE OR INTENSITY OF THE OBSTRUCTION LIGHT OVER THE ACTUAL VASI LIGHT.