There will be one line of a different color—in Silk Garden, it will probably be less noticeable over the whole scarf, but it will still be there. It really can’t be otherwise, because the yarn has to get there. Slipping the first and last stitch of the second row will make the edges neater, but won’t do much to hide color changes. What it will do is make the edge stitches twice the height of the non-edge stitches, which will make the non-working yarn much less obvious. Now, there’s a difference between the instructions and what you say you’re doing – Brooklyntweed says to slip the first and the last stitches of the second row of that color, but in what you say you’re doing, you say you knit the last stitch. This will make a difference, and it’s probably enough to account for the difference you’re seeing. What you should see on the edges is one stitch the height of two rows, alternating between stitches of each color. If what you say you’re doing is accurate, what you’re probably seeing is two stitches, one the height of each row, with the yarn of the other color running alongside them.