I am new to cake decorating and recently did this unicorn cake but I had a problem with my Wilton buttercream icing turning off white / yellow AFTER it was on the cake ?? Has anyone had this problem? Why does this happen?!? I am so proud of my cake all to have to frosting turn colors. Very upsetting!! 

did you use butter/margarine and/or use real vanilla? and how long did you mix/beat it for? 

the longer you beat your icing the whiter it will get — also please start a whole new thread to respond because:

there is some kind of new member delay on being able to "reply" to posts so please start a new thread to continue any discussion -- at some point all of a sudden you will be enabled to "reply" but not for a while -- maybe like 30 days — I think it might have to do with time and activity levels -- please respond in a new thread —

best to you

Welcome to our forum!   Sooo sorry your wonderful creation turned yellowish    I know how it feels to have something like that happen:(   You mention its Wilton icing but did you make the recipe or is it Wilton’s readymade/canned?   Unless things have changed Wilton recipe tells you to mix ingredients very slightly-just until mixed but as K8 said the longer & slower it is mixed the better especially if using part butter   Also the weather effects our work— was it hot & humid?  Was the cake in direct sun?   Along with not being mixed enough that could also do this