Allright, I'm working mostly from memory here, since Bricklink doesn't include the wands in their minifigure listings (and I'm presuming you're wanting the official wand colors that LEGO's provided?):
- Harry and Hermione both use the basic brown wands (old brown or reddish brown depending on the year)
- Ron uses a grey wand (again, old great or light bluish grey, whichever)
- Hagrid isn't legally allowed to have a wand, but is supplied with his pink umbrella in the later sets (which is just comprised of a reddish brown 4L bar plus two pink cones)
- Draco and Voldemort are both supplied with black wands
- Snape has never been officially supplied with a wand, I don't believe.
It might do you well to double check the info using Bricklink
, but I think that's it. And yes, 4L for all of them.