PLT OF A MOONEY M20E INADVERTENTLY TAXIED ONTO THE ACTIVE RWY INSTEAD OF HOLDING SHORT AS INSTRUCTED BY TWR DUE TO MISIDENT OF THE RWY AREA TAXIED ON AS A TXWY SINCE IT WAS OUTLINED BY BLUE REFLECTORS. TWR CTLR ADVISED THAT HE WAS ON THE RWY SINCE IT IS USED FOR A TXWY ONLY AT NIGHT.

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AT TUS ARPT I CALLED GND CTL FROM THE TRANSIENT PARKING AREA N OF RWYS 11L&R FOR A VFR DEP. I WAS CLRED TO HOLD SHORT OF RWY 11L. SHORTLY THEREAFTER; I WAS CLRED TO CROSS RWY 11L AND HOLD SHORT OF RWY 11R. AFTER XING RWY 11L; I APCHED A PARALLEL SURFACE THAT I IDENTED AS A TXWY FOR RWY 11R BECAUSE IT WAS OUTLINED BY RAISED REFLECTORS COLORED BLUE. I ENTERED ON THIS SURFACE; MADE A R TURN TO TAXI TO THE TKOF END OF RWY 11R. SHORTLY THEREAFTER I OBSERVED AN ACFT LINED UP HEAD-ON IN THE OPPOSITE DIRECTION. I IMMEDIATELY CALLED GND CTL TO INQUIRE ABOUT THIS CONFLICT. I WAS ADVISED THAT I WAS ON THE RWY; NOT ON A TXWY; AND THAT I SHOULD REVERSE COURSE AND EXIT IMMEDIATELY. THIS I DID; AND AFTER COMPLETING A RUNUP; DEPARTED WITHOUT FURTHER INCIDENT. THE NEXT DAY AFTER RETURNING HOME; I CALLED TUS TWR AND SPOKE WITH A CTLR ON DUTY ABOUT MY EXPERIENCE. HE ASKED ME TO HOLD THE PHONE FOR A FEW SECONDS TO LOOK OUTSIDE. AFTER RETURNING HE STATED 'THE REFLECTORS ARE THE WRONG COLOR. BLUE IS A TXWY COLOR. THAT IS A DISPLACED THRESHOLD AREA FOR RWY 11R. I WILL SPEAK TO THE ARPT MGR ABOUT CORRECTING THE SIT.' A REVIEW OF THE AFD SHOWS A NOTATION: 'RWY 11R DISPLACED THRESHOLD NOT LIGHTING. USE DURING DAYLIGHT HRS ONLY. AT NIGHT USE AS TXWY ONLY.' IN MY VIEW; THIS IS A DANGEROUSLY CONFUSING SIT. WITH MORE THAN 30 YRS EXPERIENCE AS AN AIRLINE PLT; I ASSOCIATE BLUE LIGHTS WITH TXWYS ONLY. I SUGGEST THAT THE TUS INTL REFLECTORS BE REMOVED OR REPLACED WITH REFLECTORS OF A DIFFERENT COLOR.