This is exactly why I stopped trusting what I see on my own monitor years ago. I read a while back that two different screens can show the same color file totally different, and even the same screen looks off depending on the light in the room. There's this whole thing about color profiles where one machine reads the numbers one way and another reads them a whole other way. A muddy green coming out of a teal file is a nightmare because the client just sees the wrong thing on their end and blames you. What I heard works is getting a real proof printed and signed off before the full run, so nobody's guessing off a screen. Costs a little time up front but saves you from eating a $1,200 loss like this.