Tinsel I gotta go against the grain here too - I firmly believe if not dyeing your hair is something that is really important to your DH, despite him having read all the info about how it is okay, then you should weigh up your desire to dye your hair against his fears and think about it in the context of your relationship with him. I am in the same situation as you - I am comfortable with it, DH is not, but because my desire to dye is due to vanity alone ( and his concerns are for the safety of our babe, I feel his needs/desires/fears deserve to be listened to, and so I won't dye my hair. There are going to be many things in parenting that one of you will be comfortable with and the other won't - personally I think that sometimes for the sake of the relationship you need to listen to the other person's concerns and sometimes concede, even though personally you think it isn't an issue. Plus to play devils advocate, imagine how you would feel if your DH did something which you were fearful would harm your baby, even though the risk was small or irrational - I imagine you would be really peeved that he didn't take your feelings into account? I think guys get so little input into the whole pg thing that whenever possible they should have a say and be involved, and maybe this is one small way you can make him feel like he is gestating this baby also?
Garbled I know but I should be working :) hope it all works out....