Theoretically, if the seam is pressed to the side, the seam allowance closest to the top fabric will be the only one you can see through the top.
Try it an see with scraps.
It I am sewing with a white and darker color, and want to press to the white side, I have the white piece stick out a couple of threads wider for the seam allowance so that the darker color will be completely behind the white (when looked at through the top).
Clear as mud?