Here he is, my new warrior. The mighty berserker Thorgaard Giantsbane:

http://cloud.steampowered.com/ugc/612719639794972883/8AEB62DB5F89509522973DD53F1B9B9EF4646C93/

I really wonder this myself.. I found it a bit odd that hair color sliders weren't included, since they've been in previous games, and there are so many sliders already. It makes it a bit hard to make my usual characters, since I often go for an out-of-the-bottle flaming, fire engine red (my own hair color). The 'auburn' color they have in the presets is not very red at all.. more of a dark rusty brown. Hopefully the CK will give us tools to change hair color a bit more freely. As said, Irileth has very red hair, of a kind it's impossible for a player to have.

But now it IS possible

Other colors of note are mostly from Argonian males. The males have purple, blue, dark blue-gray, green, bright/over-saturated red.

Female Argonians only unique color is a green tinted neon yellow.

Both Argonian genders share the darker red i mentioned before, and a few fiery orange colors.

I'm currently playing as a blue haired female Nord, and haven't encountered any glitches so far.