Two colour knitting

Well, I’m a fairly new knitter. I know how to knit and purl, and I can do some increases and decreases. And I’ve done a few things (a scarf, some cloths, fingerless gloves, etc. I tried a sock, but I think the pattern was faulty.)

My question is about how to do fair isle or intarsia. I’ve seen the video’s and stuff, but I’m unsure about how to start. How do I cast on with the two different colours? Or do I cast on with all one and then add in another colour after?

Any help would be much appreciated.

You cast on with one color. When it comes time to use another color, for Fair Isle you carry the two colors all the way around or back and forth; for intarsia, you have a separate strand of yarn for each section of color.