Yellow or Red Miso? I just bought some red miso and would love to avoid hitting the store again for this item. Will the flavor be off with the red? U

IMHO, it will be tastier. I prefer red to white. Yes, as Nancy said, it is "stronger", but I think you will like it.

Red miso is stronger in flavor and saltier than yellow, but and if you like it, go ahead and use it in this recipe.
I would start with half as much as the specified yellow miso, check during cooking and add more red miso to taste.
Also, look at Bon appetit for a good article about different type of miso.