Assuming Truth and Regret are old, what would young prophets like or female prophets???
Look at halo wars I believe regret is young then
Well, the descendants of the Reformist San 'Shyuum are said to suffer from genetic erosion due to interbreeding, a much smaller gene pool and a sedentary lifestyle in the Covenant. I’m sure that attributes to their aged and withered look. Although oddly enough, they’re described as seductively beautiful by Forerunners and humans in Halo: Cryptum. I assume younger reformists would look slightly closer to that.
Regret is considered young for being a Hierarch. Mercy is definitely the most elderly as he has cataracts in his eyes, has a bit of a shake when he talks and moves. I believe he is 220+ years old while Regret was only 70 during Halo Wars and 91 when he died. So really the best look at young reformist prophets is Halo Wars Regret for right now.