Stripes how to carry the colours up

He there y’all,
I am attempting a scarf pattern that has 2 colours and has varying thickness’s of stripes. I guess the best way to carry the colour is to let it hang up the side. I get the fact that I have to be careful to keep it lose enough, but can it be too loose? And when it’s finished will these loops remain? Is that ok?And when I am bringing in the new colour should I knit the 1st 2 stitches in both colours? The colours I have are black and pink so would that look ok if I did?
I’m sure this question has been asked many times, and I did look for it but couldn’t find it, so please forgive me :wink:
And also forgive me my awkward descriptions!

You don’t actually let the loops hang off loosely, you twist the 2 colors around each other a little. And you wouldn’t need to knit the old and new colors in the same row, just start the row with the other color.