AI use cream cheese frosting a lot on my cupcakes and because of the butter it's always a little yellow. I've heard of two solutions: 1) use white food coloring 2) use a tiny bit of violet food coloring to cancel out the yellow.

I'm wondering if any of you have used either trick or both? What have been your results? Which one works better?

ABoth work. I prefer using the white food coloring from Americolor or wilton. I use it frequently for all sorts of things

I use Wilton's white usually, or violet if I'm all out. Both work just fine :-)