Whenever I make purple buttercream icing (even light lavendar) I always put merenge power in it, but the color always separates and I end up with little dots of blue in my completed cake!

Any suggestions?

Thinning with milk usually helps purples stay together and keeps them from changing colors on you. Other than that, just mix really well. Maybe even let it set and mix again.

I've heard sometimes table salt can cause this too but I'm not sure.

Do you use salt in your BC recipe??Sometimes if the salt in the recipe doesn't melt it will cause spots in the icing. Just a thought!!