The term "green" has nothing to do with with a horse's coloring. It is used to describe experience in training. Someone might say, "Oh, you don't want him, he's green." Typically it is used to describe young horses. They might be broke (able to be ridden) but that does NOT mean that they are an old trail horse! Green horses should be trained by a professional horseman until they are ready to be sold to an experienced rider. Just as a warning: If you are not a professional, or being trained by one, please do not attempt to ride, or jump!, a green horse! With my lil' green-bean, I usually end up eating dirt before an extended trot! But great question!