Battery Wiring 2006 Volvo VNL

I have a truck that did not have any battery's or jumper cables. I've bought new battery's (4) nuts and jumper cables and started putting it all together and noticed that the power main cable has a little grayish cable running along side it and the negative main battery cable has one also but it's red which is screwing me up. From what I can tell they both run to this little 20amp fuse and from there I'm not sure were they go but from what I've gathered probably the ecm so my question is were do these go? they both have loops on them giving me the impression that they obviously hook to the battery's but not sure whether or not the one that runs along side the negative goes to the negative or not, I mean it seems common sense would say sense it runs along side the main negative battery cable it should connect to the negative terminal on the battery also but it's red which usually means positive power. one other detail is that those smaller wires are also a bit shorter meaning they won't quite reach to the same terminal as the main battery cable would go almost like it would have to go one battery terminal over but would be long enough to go to the other side also if that makes any sense..

 

Right, good point. I'll try that out and see what happens.. There's a fuse on there so if I wire it wrong it will blow..

 

Ok it turns out that I and most of you were right the red does go to the positive even though it's zip tied to the main negative cable.. She started right up after all was connected after sitting for 4 plus years..