Yea I dyed my hair too when I was 4 or 5 months my hairstylist said as long as the paint doesn't have amonia or whatever is called lol but ask your stylist she will know something about it but is ok to dye it:)
As long as the person doing your hair know your pregnant, and are (i believe) 3+ months it's fine.
I had my hair dyed at 5 months
I've been putting off dying mine b/c I'm scared to do it & I'm 21 wks. My students pluck out my white hair :/