Creating appealing design with flowers can be tricky. It's a matter of combining colors, textures, and plant forms in a way that is pleasing to the eye. You're right in thinking that planting the same thing in different areas can be a good thing. That's called repetition, and is one of the major principles of design. It's counteracted, by contrast, however. That means that it's also good to mix things up a bit. It sounds as though you have a start at that, with red impatiens by the door and red geraniums by the garage. The color is the unifying element, but the different plant types create some contrast. Perhaps you need a bit more color contrast, too. For example, a touch of white would complement the red and set things off.