I go with my gut on the color I call them, even if it isn’t the most logical choice based on another color having a larger presence on the jersey or whatever else. For me, when I’ve tried to go against that instinctual conclusion of what to call them, it’s another thought process I’m having to sort through in the heat of the moment and I usually end up accidentally reverting to the initial instinct anyways.
I’m trying to help facilitate a flowing game by giving guidance when possible/practical but, if they get it wrong, they (hopefully) learn from the penalty. There are too many things to watch and consider for me to want to remember a team name or call them some specific shade instead of a major color name or even really yell a specific number, unless the number is pertinent in that one player is legal and another of the same team isn’t.
I have almost always found “leave it green!” or “no hands now green!” to be sufficient. I don’t want to make it more complicated than that.