I have used it in both top and bottom with ok results. A lot of people find invisible thread in the bobbin really finicky and have a hard time with it. I mean, I don't think I have ever been able to achieve perfect tension that way - but - you can't see the stitches that well anyhow!! As long as you're not getting loose weak stitches it's fine.
What about a taupe or a cream thread? You can usually get away with an offwite or tan thread on almost ANY project. I would post some pictures so we can see what you're working with!
