Colorized infrared imagery uses special color enhancements to highlight certain aspects of the data. In this imagery, the colors represent cloud-top height. Yellow and orange areas signify taller clouds, which often correlate with more active weather systems.
You can advance the imagery by placing your cursor over the image and using your mouse's scroll wheel, clicking the image and using the up and down arrows on your keyboard, or by clicking and dragging the scroll bar down (to go forward) or up (to go back). To save a particular image, scroll through the animation to the frame you want and right-click.