When my uncle tried making salted egg, the dye he tried using never worked out well. The eggs were barely coloured and appeared ugly. He was troubled selling it to customers.
When I tried making turmeric salted egg, the golden yellow color barely hugged the egg shells, even though they were submerged in turmeric solution for almost two weeks.
A little googling gave me a solution. I need to add two more ingredients to dye solution. The salt and vinegar. The latter reacts to egg shell allowing the dye to penetrate a bit. I am not quite sure about the first. What I know is, it is also being used for T-shirt dying for a longer lasting brilliance.
For the trial, I got one white chicken egg, two small pieces turmeric ginger, one cup water, a teaspoon salt and two tablespoons vinegar. I sliced the turmeric and dropped it to slow boiling water. Waited until color dispersion was evident. Mixed the salt and vinegar and placed the white chicken egg gently.
The egg was barely half submerged and I needed to turn it from time to time until a nice deep golden yellow color was achieved. It was really nice. If only I learned it earlier, then the salted egg business attempt of my uncle would have greater chance of success.