Vampire Eye Color

I haven't read the books, but in the show we know that when people become vampires they get the nails and their eye color changes. So far we've seen blue eyes (Lestat and Gabriella) green eyes (Louis), red/orange eyes (Claudia, Armand, and Daniel), and gold/brown/yellow eyes (Akasha). However, Magnus and Marius appear to have dark brown eyes, a normal "human" eye color. Actually, now that I think about it, Magnus' eyes were actually black, so not a normal human eye color. I just find it interesting that all the vampires we've seen have lighter colored eyes, so to speak, except those two. Thoughts? Any book explanations?