You can use regular vanilla for a light ivory tint as well.
Americolor offers ivory coloring in their soft gel paste colors.
Theresa 
To make Ivory, I use half regular white crisco and half butter flavor yellow crisco in my buttercream recipe. It makes a lovely pale pale yellow, like aged ivory.
Good Luck! 
A word of warning. . .
Be careful using the wilton ivory paste. I used it on the last wedding cake I made, and the color came out much darker than I would have liked. The bride didn't seem to mind, though.
i used Americolor - Ivory for the last wedding cake i did (in photos) it worked amazing with the fondant AND bc.. my mother made the batch of bc and i thought she put too much.. but it matched perfectly..
i've never done an ivory cake before that and i thought i just looked so elegant..
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