You're not looking in the right place - those are the wires in the connector on the harness section that goes to the RIGHT bar-switch (brake lever side) - as you have found, that section of harness does NOT contain those wires. (he had identified a group of wires, none of which were the afore-mentioned green/white and green/red)
The turn signal wires come off the MAIN harness, not on that section that connects to the bar switch - they are probably in the same section of harness that feeds the headlight
You can also find those colour wires for turn signals on the harness section that goes to the LEFT bar-switch (clutch lever side) connector
I identified the colours correctly - you just need to look for them - as I said earlier every single Triumph for 20+ years follows that convention however I specifically checked the TBird diagram to confirm