What color is the mold on that wire you think is yellow but maybe is faded light green ? Usually molds color should match the source molds color it plugs to... althought I have seen batt and cluster light circuits with black molds and they still conect into the red and orange molds respectively... but wire colors still match the circuit it plugs to on these.
Just for extra info:
on 71 the time delay flasher feeds not just the ign key light but also the seatbelt warning light. Can't see if your car is 71 or 72, but I guess 71 being with the color keyed bumper?
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You can just connect it into the right mold and you are done! Connect that wire which should handle ground into a positive source shouldn't have burnt anything because is just designed to trig the flasher on to feed the bulbs from the batt positive. Being just a trigger signal it won't hurt anything, simply wouldn't make it work.
Assuming the flasher is there and in working order, you will get back that function. If bulbs are fine too of course.
About trace colors. Sometimes the trace colors are specified. I.E front turning signals, which for whatever reason become black on forward lighting harness, and the trace color meets the color they had into the cab, light green or tan, each one for each side.
It happens also similar with parking lights circuit on some years, where into the cab the wiring for them is yellow with black trace ( just like the door ground on some years... 71/72 for example as we can notice ) but as soon it leaves the cab these colors are reversed and become into a black with yellow trace.
And more info:
since 73 the door ground circuits were simplified from 3 wires 71/72 had ( black, yellow and yellow traced on driver side door ) into 2 wires ( black and yellow, not anymore the yellow traced ).
