When I clicked on my rider today she changed skin tone and hair color, I did not do anything to change her appearance before. She used to have red hair and base 1, now she has black hair and base 3.

The skin color of both of my riders changed as well.

Mine are changing as well. Ross 101 was the basic default hire a rider: black hair, brown eyes, pale skin and now has brown hair and one of the darker bases: https://horseeden.com/rider.php?id=2599586

I believe some of my other riders changed appearances too but I do not remember their original looks as well.

This should be fixed now, thanks!

Both of my riders changed appearance again.