I followed the instructions given by wrique in this instructable using ferns and red onions. We also tried using iris petals, carrots, parsley, Japanese Kerria, Mahonia, and ice plants.
Step 1: Using different plants
We followed wrique's instructions but used purple iris petals, carrot peelings, Japanese Kerria, Mahonia, and parsley in addition to the red onions. The Kerria, Mahonia, ice plant, and carrots had no real color affect on the eggs, but they did leave some cool stenciled designs. The parsley and purple iris left some color.