Tho I do remember a mod that offers moving eyes to better heads, so those could be easily alterable.
exactly what came to my mind and here is a link:
http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=7710
for the easy alteration thing, a passage from the description of the mod:
This is a MESH REPLACER for 171 of the head meshes found in Better Heads.
It replaces all the heads with new head meshes that have EYES that move.
can't access nifscope right now, but in the download there was a .dds-file: http://img256.imageshack.us/img256/6015/screenshotuzn.png
seems as if you could adjust the eye color, but you would have to know the specific eye...
checked the readme briefly, it has some information on eyeball-scaling if you want to replace some of them (seems the eyeballs scale in a race-height-weight-dependent manner or something)
so, all in all, maybe it's easier to simply pick a nord-face texture and edit just the eyes in that particular .dds-file