Here the colors of the sky are set. Everything has been blended in anticipation of the clouds, which will fill the space between the bottom edge of the sky including the open section down to the horizon. I have learned that in some cases it is better to leave a void in the sky area when you intend to put brighter colors in the open location. I can sit back and evaluate what I have to do. I know where I want my color to explode from the photograph I have been looking at all of the time.