IIRC it was brown. Blue and brown are pretty much universal. Yellow has the timing retard function, and red is a DS1 unit that was only used for a short time in Kalifornia. The box doesn't care how many cylinders, if that helps any.
If you use the yellow grommet, you just plug in the one side and you can leave the retard plug hang. I had a yellow grommet when I converted my Sprint to DS2. I just dead ended the wires and put them in the harness I built. I was planning to use the retard for something in the future, but never got around to it.