Tamar Tessler wrote:

Dear Rabbi,

We have a custom in our family to color eggs for Lag B'omer, and we know of others around the world that have this custom too. Yet nobody seems to know the origin or source of it. Some people I have asked suggested it is taken from a pagan custom, G-d forbid. Can anyone shed light on this please?

Dear Tamar Tessler,

I asked your question to Rabbi Eliezar Demari of Jerusalem. (His parents came to Israel from Yemen in 1949.) Rabbi Demari said that in Yemen, the Jews painted eggs in honor of Purim. They sent these eggs to friends as mishloach manot gifts and ate them at the festive Purim meal.

The Jewish community in Yemen was isolated for centuries, and they can trace many of their customs back to the time of the First Temple, so it's clear that they didn't adopt this practice from any other culture.

Rabbi Demari also noted that it's conceivable that egg-painting was a custom among European Jews, and that they stopped doing so when it was adopted by other religions.

We see the same concept regarding a stone altar: Although Abraham, Isaac and Jacob made stone altars, the Torah later forbade making them because the pagans had begun making stone altars for idol worship. Thus, we see that a "kosher" custom gets spoiled when it becomes a pagan custom.