Im a fairly new quilter and I have a really hard time staying in the ditch and I get frustrated and critical of my work. I have started using a serpentine or zigzag stitch when I stitch in the ditch. I also do a lot of shadowing the ditch (more work) For color, I would use a color that blends for the bobbin and white or lt gray for the front (regular quilting thread). Keep it simple, you want your blocks to stand out not the quilting.