Yes, as long as you're in a well ventilated room it's fine.
I just ask my OB the same thing. She said as long as it's well ventilated in the room it's safe anytime during pregnancy. Not muh chemical absorbs through the skin.
i think it is as long as yu do it outside or something so yur not breathing it alot but i also heard sometimes the dye doesnt come out the color yu wanted it cuz yur hormones... idk if thats true tho i havent attempted to dye my hair as much as i would like to cuz then my daughters dad will say all this stuff nd id rather not hear it haha nd plus im tryna get my hair to get healthy nd grow again