How is Doppler information displayed?

The velocity may be displayed in a graph of velocity versus time (spectral Doppler), or it may be displayed as colors on a scale (color flow Doppler). By convention, blood flow toward the transducer is red, and blood flow away from the transducer is blue. Spectral Doppler generally samples one given area, while color flow Doppler may simultaneously depict flow over the entire imaged area.