Help with knitting horizontal stripes, Please:)

Hi All, I’m new to the site & am hoping for some help w/a simple question. I am knitting a baby hat which has horizontal stripes, 2 rows in width. What is the best way to join the colors? Intarsia? Just join new thread for each stripe? Any suggestions would be welcome.

Flat or in the round?

The easist way is to just start knitting with the new colour (yarn B), you may want to tie it loosly onto your existing yarn (yarn A) to hold it in place until you weave the yarn in later.
I would not cut yarn A but would leave it hanging. Each time you come to it, weather in the round or knitting flat, carefully twist the yarns around each other to ‘carry’ the unused yarn up the side (or creating an almost invisable colour change at the start of each round). When you want to switch back to Yarn A just drop Yarn B, Pick up Yarn A, bring it around Yarn B and then start knitting with it.

This prevents lots of ends to be woven in and keeps things nice and neet and tidy.