need help with a simple wiring issue
 

I lost the plug that goes on my 862031 alternator during an engine swap. I found an aftermarket pigtail but it has 2 black wires. not red and purple lihe the one i lost and the wires on my harness are red and purple.this is on a 1999 7.4l MPI mercruiser. im sure they used it in other places as well. does anyone have one they can look at to tell me which side is red and which is purple

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http://s172.photobucket.com/user/tim...k7te.jpg.html?

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