In that case, you can dye your hair. Just make sure it completely dries and you wash it off (what Carolyn said above).

I would say that they should be fine now. It happened once and they didn't have any bad reaction to it. Just try to avoid it next time.

Most likely nothing will happen. But if anything does go wrong it would probably be the usual symptoms of a sick bird - fluffed up, inactive, not eating, poops look wrong.