73 Mach 1 Coil Wiring

I don't think they meant that wire was coming from the tach. I believe what it was meant to point out is there was a tach option on some cars and that power feed to the coil is either pink (no tach option) or red w/green stripe (has tach). It should be your power feed and should go back to your start relay. Generally a tach wire is solid green.
Verify that red/green wire by flipping your ignition on and putting a volt meter on it and you should get 12v or a little less if resisted.
There are others on here that know the 73 better than me though and im sure will chime in on this for you.