I’m knitting a scarf and want to use purple and black either by knitting one row black one purple or one loop black one purple. The problem I found with knitting each loop a different colour is that it changes the pattern and twists the two different yarns so much :x .
Do you mean that your working yarns get tangled?? :? Well, if that’s the case, I don’t think you’re doing anything “wrong”; that’s just the woes of color work. To keep my strands from getting twisted around each other, I pay close attention to my turns at the end of the work. If I turn my work clockwise after one row, I make sure to turn my work counter-clockwise after the next row. Then clockwise, then counter, then clock … etc. That keeps my strands in order.
Horizontal stripes are the easiest. Do two rows with one color, then drop it, and do two rows with the other color, repeat.
The easiest way to alternate stripes vertically, is with Fair Isle technique (see video in the Advanced Techniques section). The back will have loops, but it might not look bad.
Remember to avoid doing the scarf in stockinette stitch (Basic Techniques/ More page), because it will curl into a tube.