Any CarCurus with a strong background, electrical Diagnostics

This question is for any Cargurus, what's the strong background
troubleshooting electrical issues:
I don't kiss and tell them a beautiful I'm working on know from experience
when you buy an aftermarket pigtails Auto Parts there always not the
matching colors so I ran all the out of the print out my map and cut one wire
at a time. After doing so I attempted to turn the car over no click no start got
my test light meter and a Power Probe and over my work. Found that one of
the pigtails had 12v on the (G wire) so i took another wire to ground the body
to see if it will turn over nothing i ran my ground to the old ground (I think it
has a short in thevl harness somewhere since it shows 12v) all 3 wire
together it here the starter for the first time can anyone explain why and how
this is possible.. just want to get some more knowledge electrical
diagnosing is not really a strong background for me. I will have pictures from
the printout of all data and the OE plug