I have a wedding cake to do and the bride wants an off white color. I will be using premade fondant and gumpaste which is white. What can I add to give it an off white color?

I would think a tiny bit of brown coloring would do it.

you can try adding a very small amount of ivory for an off-white tint or a tiny bit of golden yellow for cream.

HTH

thank you. I was thinking that I would try the ivory but was not sure how much. I tried it with buttercream and it was way too dark! I used too much!

You can also just buy ivory fondant, unless you're trying to just work with what you've got...