There's really no telling what will happen in individual cases.
Mine grew back curly, but it's straight again now - I don't know if that's from the weight of it now it's long again though.
Some people's hair grows back a different colour; generally though, grey stays grey unfortunately.
Most people I know who've had chemotherapy have had their hair grow back pretty much the same as it was before; some have noticed an improvement.
Mine is thinner than it was before chemo, but as I had very thick hair that doesn't matter much.