Backwards knitting in the round

I want to make a headband in the round that has a cast on of 99 stitches, 66 stitches of one color and 33 stitches of another color. After casting on, how would I join both colors? Since I’m working in the round when I come to the color that has the 33 stitches, would I work those stitches as normal and would I have to knit them again backwards in order for the stitches to be in the correct position when I continue working the rest of the stitches? I saw a video of something like that and I didn’t bookmark the video and now I’m having trouble finding it.

Welcome to KnittingHelp!
You will need to do a technique for intarsia in the round. You’ll be changing colors and using short rows to ensure that the color you need will be in the correct position when you come to that color change.

I’ve done this for a sweater using German short rows but you could use whichever technique you prefer to the short row.

The 33 stitches I cast on will always be knitted the same color throughout
the entire headband. What I’m trying to make is an American flag headband.
The 33 stitches will be blue and the 66 stitches will be an alternating red
and white stripes. Could it be possible to achieve using the intarsia in
the round video you linked me?

Yes, that is the technique you would use for large color blocks in the round. It’s just too many stitches to carry the unused colors as floats across the back.
An even easier way to work this of course, is to knit flat and seam the headband.

Thank you. I was trying to avoid seaming.