Here's a video How to Knit a Scarf
that shows a very simple color change. Demonstrated on extremely huge needles too! Only thing I'd do differently is IF you LOOSELY knot the 2 strands together as demonstrated, when you go to weave in the ends I'd unknot the strands first; cross the strands to cinch up the hole then weave each end in back in the direction it came from. Ok that sounds complicated... it's not.
Oooh oooh and there are several yarn joining videos here on KH -- Scroll down on this page to the section "Joining a New Color Yarn"
. She shows you how to seal up that hole too. The "Duplicate Stitch Join" video there seems like the type of join your pattern is explaining. The video is great, but a little dark and small.