I can't say why they would order something other than coffee during their meeting (people do that), but your version seems a lot more complicated. It seems more likely to me that they just ordered multiple things as the meeting went on. And who said they're margaritas anyway? Even if they are, isn't it possible they weren't made with the fake garbage that gives them the vibrant colors people expect? Just seems like a massive jump to make from such little information.

From a top result for margarita search. I can easily see it being a little more transparent if they didn't go super heavy on lime. Not everyone uses fake coloring in their drinks. There are also clear flavorings if these aren't lime.