Echoing what Peckish said, sometimes using a thin natural muslin as a backing layer can work well. With white fabric, I find sometimes using a bright white underneath it (whether batting or fabric) actually emphasizes the issue, while off white softens it. Same sort of reasons why wearing a beige bra under a white top is a better solution than a white one.
The white seam is one of the reasons I prefer to press my seams open, just can't stand what happens when you put two pieces of white together with a side seam.