Heat a saucepan of water so that it is warm, but not boiling.
Divide the water into individual heat-safe bowls. Each bowl should contain about a cup of water, so that an egg could be fully submerged.
Add a few drops of food coloring — 8-10 drops is a good starting point. Add more if you'd like a deeper color. If using gel food coloring, it usually comes out of the bottle in blobs rather than drops. Start with 2-3 blobs and go from there.
Dip hard-boiled eggs in the dye and allow to soak for at least 10 minutes.