Does anyone know what combinations of the Americolor gel I need to use to get both fondant and buttercream a blush color?  

AWhat about the slightest use of rose color. Not sure.

I would use orange and pink. I would make up a small amount of each colour fairly deeply, and start adding this bit by bit to the white icing, until you get the colour you need. I would do this for both fondant and BC.