So, for green I used a few handfuls of fresh baby spinach leaves and simmered them in a pan with about 1.5 cups of water for 10 minutes. When the water was starting to look green I turned off the heat and strained the leaves through a sieve, squeezing out some more colour.
For purple I used a small punnet of blueberries and simply put them in a dish in the microwave with a few tablespoons of water, for about one and a half minutes. Then I mashed it into a pulp and strained the purple juice through a sieve. You could mix the pulp into yoghurt or make it into baby food. I topped up the juice with a little warm water and stirred it through.
For yellow I used a few tablespoons of turmeric, a bright yellow/orange spice used commonly in Indian dishes. This was really simple to create! I just stirred in about two to three times as much warm water to the amount of dried spice and stirred until it was dissolved. It made a lovely, thick liquid, reminiscent of old school powdered paints.
I put the new dyes into old jam jars which double up as nice paint pots with lids. Here’s the result when they are painted onto watercolour paper.