[VetteVet]

If you take a look at my second diagram above, it shows the directional switch wiring in the second group from the top. GM used the same wiring colors in most of its vehicles in the 60s and 70s.
The power feed wire for the turns is purple.
The left turn is colored yellow.
The right turn is dark green.
The right front signal is dark blue.
The left front is light blue.
And the dash indicator is also blue.

The respective wires should show continuity at the switch between the front and rear signal lamps. When the selector is moved to left turn you should have continuity between yellow and light blue. And right tun gives continuity between dark green and dark blue. The hazard switch will give continuity between all four.
If you have an indicator in the dash cluster it will show continuity as well.
It appears that the wiring is crossed between the dark green and yellow wires at your switch connector or in the switch itself.
What does a fight turn give? if you get the dark green and dark blue wires then the front signal wiring is ok and you may have the rear wiring crossed.
Hope this helps. VV