I posted some info about a 5 wire SignalStat model 700 here . Your colors may not be the same but I imagine it works the same.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.