Paint price.

OK just got an email from the body shop thats doing the Duster.They have given me a quote on the body work and base clear some time ago,I am fine with that.So I went with them to remove the under coating and paint the undercarriage,there quote was fine.Wile back i reminded them we wanted body color for undercarriage about 3 weeks ago.The email they sent that we quoted for black paint for the underside,not in writing tho.WTF is the difference from black vs blue.What would you do.I hope the is not going to be another body and paint from hell again.Thoughts please.