HOW TO: Knit a two-color I-cord Christmas tree garland?

I am trying to knit a 2-color I-cord or something similar for a Christmas tree garland. I spent several hours looking through google but I can’t find enough directions for me. I dont have a specific thing in mind. I think it would be really neat if they could be knitted to look like they were twisted together but that may be beyond my skill level(beginner) or impossible.

I found a pattern for I two-color I cord on this site but my problem is I don’t know how to add the second color on. Do I just knit from the string or is there something special I need to do to add it? Any info or ideas would be much appreciated.

You can just start knitting with the new color. Let the tail of the old color (about 4-6") hang outside the I cord and do the same with the tail of the new color. You can snug up any loose sts and weave the tails in later.