Knit one color yarn then add another color

I am knitting legwarmers and am using dark brown yarn for 9 rows then switching to beige and knitting it for 9 rows my problem is the dark brown is showing up when I overlap the beige yarn is there a video somewhere where I can see what mistake I’m doing or can someone tell me what I’m doing wrong.
Thank you

Are you doing a stockinette stitch? If so are you adding the colour on a knit row? If you add it on a purl row, it will show on the RS. Try adding your next colour on a knit row. The only place it will show then is on the WS. Good luck!

Another idea… If you are doing ribbing, add a row of the new color in plain knit, on the right side, or purl on the wrong side before resuming the rib, it will make the change crisp.