There is a mode similar to color Doppler that you may encounter called Power Doppler. This mode does not show up as red or blue on the screen but only uses a single yellow color signifying the amplitude of flow. So you can’t tell if the flow is going towards or away from the probe given that it has only one color. It is more sensitive than color Doppler and is used to detect low flow states such as venous flow in the thyroid or testicles.
