Pela’s name day is May 4, the feast of Pelagia.
Churches that follow the Old (Julian) Calendar keep the same feast on May 17 of the civil calendar. See everything commemorated on May 4.
The saint behind the name

Pelagia
May 4, Holy Woman, Πελαγία
The Holy Martyr Pelagia was a young Christian woman of the early Church who suffered during the persecutions of the pagan emperors. Refusing to deny Christ or to be turned from her purity, she gave her life rather than betray her Lord, and the synaxaria honor her steadfast confession.
Also celebrating on May 4
These names share the feast, many of them other forms of the same name:
What to say on a name day
The Greek wish is Χρόνια Πολλά (Chronia Polla), “many years.” A call or a short message on the day is what people remember. See name day wishes you can send and what a name day is.