In the program that you use to knit, you will have assigned certain yarns to certain
feeders. When you thread up your machine you should adhere to these; not
following the assigned pathways will create a different outcome than you
might expect. Of course, if you’re feeling adventurous or you want to swap
colours without programming it, you can swap pathways as much as you like. If you switch around pathways, always do so with the entirety of the path from start to end. You can find an overview of the pathways here.
In the most left image below, the green design is assigned to feeder 3, and the pink
background is assigned to feeder 4. To get the right result, thread the green
yarn in feeder 3 and the pink yarn in feeder 4 (most right). If you switch them
around you will end up with reversed colour (middle).