ch-ch-ch-changes!

so you've finished your foundation chain, you've gone a few rows and want to change to a new and more exciting color.....

you've arrived at the end of your chosen last row as shown here:

chain 1 as shown here:

hold the tail of your yarn out a bit and snippy snip as shown here:
((don't cut the tail too short, we have to weave it in later))

now pull the tail you just cut through the loop on your hook and
pull the knot taut.  (that's tight to you and me).
as shown here:

this is called "tying off"

turn your work so that the knot is on your right.

(sorry, lefties, i don't have a clue how to help your kind)
put your hook into the first stitch.
as shown here:

pull your new color through while holding on so the end doesn't come through too.

as shown here:

keep holding on to your new color, chain two (since we're doing half doubles).

like so:

continue on a few stitches to get your new color settled in to the new neighborhood.

leaving the ends out like so:

when everyone is settled and getting along, tie the two colors together in a double knot.

now, GO!  go like the dickens!