I'm from Canada as well, and used to buy Superstore's No Name brand white margarine, but they no longer carry the product since they cannot find a supplier/producer to supply/make the margarine for them (have called and searched). This was my way of making White Buttercream - no Crisco added, that stuff just leaves a nasty film in your mouth (my opinion). I am so distraught on how I'm going to still use my non-Crisco recipe to get a white icing. I saw on a search to add a touch of blue or violet food colour to the yellow-tinged icing and it's supposed to cancel the yellow colour out - anyone heard of this or tried it?? Oh, BTW Canadian white margarine bakers, if you find white margarine at your Superstore - buy it all...haha
Yes I have tried that (got it from a tip here on CC) and now I do it all the time. It helps a lot! I make an all-butter icing and it has a yellow cast to it. Just add the smallest drop of violet to your BC. You can also add some titanium white food coloring to whiten it up a bit. doing both of those things my icing is still not WHITE white.