Roan color question

I don't post often, but I read here almost every day. I had a thought on the way to work yesterday morning. It was before the coffee kicked in. I drove by a field with some horses in it. I saw one I thought was black till I got closer, and realized it had a frosting of red roan over the hips and shoulders. Pretty sure these were quarter horses. But then I got to thinking, what would roan on a black chestnut look like? I've seen the amazing pics of the black chestnut arabs, and the morgans in the gallery. Would they look blue from the hair being black, or world the red base coat color come through and make a red frosting over them. Also, has anyone got a pic of this happening. I thought it was pretty fascinating at 8 in the morning running on too little coffee, and too little sleep from being addicted to mare stare.