There is a quite lengthy post here regarding using real butter in your icing. I DO like the flavor difference, but I currently use the snow white Wilton recipe, primarily because I like how my colors are true since I'm adding them to white icing, not a yellowish icing. When you use 1/2 crisco and 1/2 butter are the colors affected?

I use a brand of butter that is a very light yellow. After it's mixed for a few minutes with the shortening and powdered sugar, it looks white. I would try you're recipe with butter. See if the color is white enough for you.

I use butter in my icing and don't have a problem getting the colors I want. Wilton does sell a product that you can use to make your icing whiter or lighten up your color if it gets too dark.

Well, I have always used half butter, half shortening and real brown vanilla - for more than 30 years. Other than getting a true white, every other colour comes out perfectly and there is absolutely no effect on getting the true colours.
The Wilton whitener product, here is a caution, if you read the label, you are only supposed to use a few drops of this. It is a bleach and probably not a good idea to use a whole lot of it as some folks do.
Apparently "Land "o Lakes" butter in the U.S. has very little colour to it and it might be your best bet for the whitest icing.
Most butters do have some yellow colouring actually added to them. Cream is slightly off white. Personally I find that if you use the clear vanilla with the half butter half shortening recipe and milk and cream, well it is almost white and not so off that it is a problem.
Genereally, I find that folks don't care about how white the icing is, once they taste the difference with the butter in the icing, they go for it every time. I have yet to have a customer choose the all shortening icing over the half butter one, once they taste it. I always let them do a taste test to determine which icing they want, most especially with those that think that they want a white-white wedding cake or such.
Hugs Squirrelly Cakes

Interesting, upon reading up about it in laundry soaps etc, basically it says it works with the sunlight to whiten items. Which further confuses me about it being used in sunblocks, but no matter.
Also, heehee, haven't used it in years, but my old bottle refers to it as a whitener. Unfortunately, the bottle is worn and I cannot read the ingredients, but it said to add 2-3 drops only. Just looked at the new bottle I bought and it says white white, liquid color whitener, so I suspect they are two different products, the newer one having the titanium dioxide in it. I also note that it does not limit what you add to 2-3 drops. So it appears that I was talking about the old version and this one is totally different.
My apologies, I stand corrected. You are correct. Gosh, my old bottle goes back to the 70's or 80's, haha! And almost full, shows you how much I was impressed with it, haha!
Thanks for clearing that up.
Hugs Squirrelly Cakes