How do you cast on with two colors?

Hi everyone! I have a question for you…I was watching the video for fair isle knitting with two colors, but I don’t know how to cast on with both colors. Do you hold them together as if you were tweeding, or do you alternate colors? I’m trying to follow a chart but I’m having trouble getting started. Thanks!

Amy
:think:

Usually you cast on with the background color only and then introduce the second color when it’s called for.

Wouldn’t it also make the cast on too bulky?