When I bring the object closer to my ultrasonic sensor, the RGB light turns from green to red (radar project). I want the mit app inventor to be green or red depending on whether the RGB light is green or red.
That seems like it should be doable. You'll need to occasionally read data from the device using a clock component and then update whichever component you decide to use for visualizing the data. It could be done as simply as having an empty label with a changing background color, or something more complex that involves drawing on a canvas.