How to knit raglan sleeves a different color than body

I would like to knit a baby sweater to look like a school colors sports jacket. I am trying to make the sleeves a different color than the body so in the pattern when I knit to 1 stitch before the marker and increase 1 stitch after the marker there needs to be a color change. Here’s the question how do I make the color change smoothly? Do I carry the body color on the back of the sleeves?? Or am I knitting from seperate balls of yarn?? I am very confused! Any advice will be greatly appreciated. -Diane (PS.- I am just using a raglan sleeved baby cardigan pattern, there are no directions for color change.)

You need to use separate balls for each color section and twist the two colors around each other at back when swapping over.
This ‘Intarsia Method’ video shows you how.