As the mom of kids who refuse to live in a world of black and white, I have started to resort to finding alternatives to food dyes. You can find out why my family avoids food dyes at all costs here:
16 Natural Food Dye Alternatives
Raspberries, Beet root, pomegranate juice, cranberry juice
Pumpkin, Carrot Juice
Turmeric powder, saffron flowers, egg yolks, butternut squash
Spinach or Kale Juice, matcha powder
Purple Potatoes, Blackberries
Keep in mind you want to use small amounts of each coloring. These are foods after all and since they are being juiced, their tastes will be strong! Start out with a little bit at a time, as you can always add more as needed.