In two weeks, my baby will turn one year old (sniff!).  We already have three (maybe four) different little parties planned for her - meaning three (maybe four) different cakes for me to make.   This presents a small problem for me:  my aesthetic desire to make cute cakes for my daughter is bumping against my vehement refusal to use any artificial dyes.
We cut artificial dyes out of our diet a few months ago, to see if it would help with Abby's behavior.  The difference has been dramatic - she still has her moods and her tantrums (she is 3 1/2, after all!), but the tantrums are not endless, she can find her way out of them, and she engages more with other people.  Frankly, I even notice a difference in myself - the last time I had something with dye in it, I was so irritable and crabby the rest of the day and could not get out of my funk.  It took me until that night to make the connection - I threw out the rest of the dyed stuff in the house that day.
So with two weeks to go, I decided to try out some natural alternatives today.  I've bought the 
India Tree dyes, but dang, they are expensive - $19 for three small bottles of dye!  Sometimes they will be necessary, but I wanted to try a home-brewed alternative.  I was fairly pleased with the result:

Clockwise from the top, the food I used to dye was:  turmeric + beet juice, turmeric, pomegranate juice, paprika, blueberry juice, beet juice, and avocado in the middle.
I made a big batch of my favorite buttercream frosting (the Cook's Illustrated recipe - 2 1/2 cups confectioner's sugar, 2 1/2 sticks of unsalted butter, 2 Tbsp of heavy cream, a splash of vanilla, and a pinch of salt) and added some dyes.  My thoughts:
The spices (turmeric, paprika) added the most easily, but leave a hint of their flavor behind.  Not as badly as I thought they would, and I would definitely not hesitate to make yellow or light orange this way.
The juices (blueberry juice, beet juice, pomegranate juice) yield the best tasting frosting, but their sheer liquidity is a problem.  I had to stir in a lot of extra sugar to compensate for the liquid, and they are still separating a little.  For a "real" cake, I would probably try my hand blender to really emulsify the liquid in.
The avocado actually works well, but tastes avocado-y.  I should have pureed the avocado better before adding it in.  It is a nice green, and I would probably just stick to using it for accents, like flower petals, rather than trying a whole green cake/cupcake.
No blue - I thought the blueberry juice would be closer to blue or purple, but it's really just magenta.  I Googled and found some people use red cabbage or onion skins, but... ew.  I can't imagine frosting my cake with water that cabbage was boiled in.  If I'm desperate to make something blue, I'll use my India Tree dye.
Forewarned is forearmed, and now I have some better ideas for cakes for Lizzy - clearly, nothing bright red is going to happen, but I think some beautiful sunflowers (piped around chocolate cookies) may be in our future.
(
Interested in the controversy around red dye #40?  Red Dye Free has a great list of links along the side bar.  If you suspect your child may react to dye, try cutting it out.   It's made a big difference for us.)