Is it normal to have some white hair in your mid 20s? Why does it happen at this age, I thought it would start mid 30s or 40s.

Also is it true that if you pull out white hair, more white hair will grow?

White hairs can start to appear at any age, mid 20's is a little early but not uncommon.

If you pull a white hair, it grows back white, but more white ones do not appear just because you plucked one.

If you keep pulling that hair out you will cause root damage. I would rather have gray hair then no hair.

Yeah, white hair can come in at any time. I just noticed my first white hair last year when I was 25. When I was in high school, I had a teacher who was 27 and he had salt-and-pepper sideburns! It's no biggie, so stop plucking them out! ;)