Need help in making design in round

Hi All,
I m making longies for my DS. It is started from downand knitting in round. I m done with legs and now I want to make a truck on the bum and it is where I got stuck. If I m using a new colour and knitting in round the thread of new colour is in the other corner, now how do I use it again. Do you guys cary that thread along the knitting or do you cut the thread after every row?
Pls help.

You’ll need to do that part flat really. What you’ll be doing is intarsia and intarsia is done flat. You can do it fair isle style in the round, but that is often not satisfactory because the contrasting color yarn sometimes shows through a bit when you have to carry it around the entire project.

What you can do is separate the back and front and do each part flat then seam the sides.