Reply to "My flooding tends to mottle"

I'm a little late to this conversation, but I used to have problems with mottling also.  I use pasteurized egg whites and confectioner's sugar only.  I figured out that when I thinned the icing with water it mottled. If I need to thin it now I use more egg white and I have not ever had that problem again.  I use various types of dyes, mostly Wilton and AmeriColor, and was having trouble with both until I stopped using the water.  I mix my icing a little on the thinner side and then add extra sugar until it's the correct consistency. Hope this helps!