I discovered a wonderful selection of European egg dyes at our local toy store. We bought some traditional dyes but you could get metallics & glittery ones also. The boys helped me create a glass of each of the 5 colours in the pack (mixed with water - great for practicing their pouring skills - & a few tablespoons of vinegar - Hug is practicing using the measuring spoons).
A hard-boiled egg goes into the yellow...
We were staying at the house of friends when we did this & I couldn't find a needle to blow out the eggs so we cracked some & dyed the cracked halves also.
Later, I did manage to blow some eggs but they just wanted to float! These cracked shells sunk.
Today, I was googling about & saw on Martha Stewart that you should dye or paint or decorate your raw eggs *before* you blow them to solve that floating dilemma. Genius!