interesting story behind window top right tiny buttons

While working on the new interface, Jobs would sometimes suggest what at first seemed to be crazy ideas, but later turned out to be the good ones. At one meeting, he was scrutinizing three tiny buttons at the top left of every window. The three buttons were for closing, shrinking, and expanding the window, respectively. The designers had made all the buttons the same muted gray, to prevent them from distracting the user, but it was difficult to tell what the buttons were for. It was suggested that their function should be illustrated by animation that was triggered when mouse cursor hovered over them.
But then Jobs made when seemed like an odd suggestion: that the buttons should be colored like traffic stoplights: red to close the window, yellow to shrink it, and green to expand it. When we heard that, we felt that was a strange thing to associate with a computer, "Ratzlaff said. But we worked on it for a little while and he was right." The color of button implicitly suggested the consequence of clicking it, especially the red button, which suggested "danger" if the user clicked it and didn’t mean to close the window.