I have Taken the original RJ45 plug off the end as this was damaged and when I came to put the wires into the new plug after stripping back the outer covering the wires are diffrent colours, on the old plug they are
pin 1 Blank
pin 2 Black
pin 3 Blank
pin 4 Green
pin 5 Black
pin 6 white
pin 7 Blue
pin 8 Blank
But the only wires I could find are Black,Green,Red,White and Blue so in need of some help chaps as in the manual on page 8 there are no coulor code for the wires.
I have the same colors as you in the “old plug” . Opening the mike, i discovered that only 1 black was present and one wire was bare (probably the gnd) This sould be your mysterious red ( situated pin 5).
pin 1-Blank
pin 2-Black
pin 3-Blank
pin 4-Green
pin 5-Shield/this was the other black
pin 6-White
pin 7-Blue
pin 8-Blank
The pin 5 wire when it leaves the factory just has a short length of black covering on it so when you come to replace the RJ45 you tend to cut this off and your left with all the colours and the shield which is the other black.
So the red one you do not use, so I would make a note of this just in case you need it Chris.
I think the best way is to not cut the RJ45 off but brake the plug open and try and not damage the wires and then put them into the new RJ45 that way you don,t get them mixed up.