Why does my buttercream after putting in the fridge to crust over look two tone. One cake is pink and the other is purple. They look like the colors didn't mix well and it looks like the white from the buttercream is peeking thru. that's the only way I can explain it. When I put the color on it looked fine now it just looks like there is white in the colors. Understand? What might that be?

when i use water on my spatula to smooth colored buttercream, it does that so i'm thinking maybe you are getting condensation in the fridge that is causing that?