I mostly work in fondant but recently did a three tier wedding cake that was finished in buttercream. Yikes! The ribbon was a lovely deep wine colour and the oil from the buttercream leached into the ribbon and changed it to a darker colour! Luckily after the initial horrilbe patching, the whole ribbon changed but what a scary way to learn a hard lesson! I have now heard of several methods to prevent this so thanks for bringing it up :)
Raewyn, Sydney, Australia https://www.facebook.com/cakesbyraewyn
