Either paint them different colors or place a Cable Anchor between them.
Tip on placing AE2 microparts: If you right-click on any particular side of an existing micropart bounding box, the micropart you're trying to place will go on the side of the full block facing the side you clicked; unless there's already something there, in which case, it'll go in the adjoining face of the next block over.
Example: Say you've got a straight line of cables running north-south. Clicking a cable anchor anywhere on it will place the anchor on the side of the cable, which isn't useful if you want to split the cable (if you're making a subnet, for instance). However, placing another anchor on the north or south faces of the anchor you just placed will place it in line with the cable, splitting it. Clicking the same exact spot with a third anchor will place it in the gap between the just-placed anchor and the now-disjoint cable, which I think just looks a little better.
Also, if you place cable anchors horizontally, you can climb them like ladders.