I am going to be molding a few fondant pieces that have some small areas of white on them. Instead of molding them with white fondant and then having to paint most of the piece in colors, is there anything I can use that will paint white over areas that are colored if I use colored fondant to start with?

I think I would mold it with whatever color you are working with and then work in the white fondant detail afterwards. Honestly I'm not sure how well that will work but I know it would work better with modeling chocolate than fondant.

I just purchased some white americolor recently. But my favorite to do white on figures is just plain ole royal icing because you can make it as thin or as thick as you need.

White Americolor, not diluted with anything, works just fine for small details on color.

I use the white Americolor undiluted all the time for small white details.

Wilton's white will work too, if that's all you can find. But store the bottle in a baggie, it always leaks.

Wilton's white will work too, if that's all you can find. But store the bottle in a baggie, it always leaks.

That's funny!! and so true. it leaks!! you would think they would have fixed it by now. I use white wilton coloring also it makes your fondant very nice bright white. It does take longer to dry! than any other color.

I laughed when I read about the wilton whitewhite leaking, so true!
CK also do a white paste colour, if you can't get the other brands mentioned. Royal icing would be a good alternative too, as suggested already by someone.