Yes, that can be the case
But its usually Red + and Green -
Not familiar with yellow being used as +, but never had a 1984 Ranger
And just FYI coil "-" is not a ground per say it is the control signal that sparks the coil
Coil gets 12volts with key on, on "+" terminal
The distributor/module connect and disconnect the "-" terminal to spark the coil, it sparks every time it is
disconnected
"-" is used because when there were points inside a distributor it was just easier to use "-" than "+" because of possible shorts
The points connected and disconnected "-" on the coil
This type of Electronic ignition just replaces the points opening and closing with transistor opening and closing to cycle "-" terminal on the coil, so no moving parts to wear out, although these can wear out,