<prompt> The intensity of colour in Doppler is determined by -Direction of flowVelocity of flowStrength of returning echoNone of the above  <response>: Color intenstiy indicates the relative velocity of the red blood cells. yellow white represents the highest velocity for flow directed towards the transducer. green white represents the highest velocity for flow directed away from the transducer. Doppler effect is due to shift in sound frequency as the sound as reflected from the moving Red blood cells. 