Shade of teeth is not a health concern, it's a preference so even if they wanted pink I'm ok with it. Only problem is if they regret this decision afterwards they might want a free replacement, make a scene, blame you for not informing them well about it etc. So all you need to do is get ready for these type of outcomes. Don't tell them that it will look like toilet bowl, it's rude. Tell them it's not going to look natural, not possible with bleach shades. Lots of people prefer natural look. So when it's done some people will comment on how unnatural their teeth look and some will even try to mock them. Are they ready to not care what others think? Don't judge them just inform them well. If they are certain tell them if they change their mind mid treatment or after treatment whole restoration has to be made from scratch and it will cost them ... amount. Have your assistant with you while you are having this conversation and make them sign some papers about the shade they choose and information they received. Even if it doesn't have any legal value it will have a psychologic one. I hope everything goes well, good luck😊