Color ultrasound refers to color Doppler ultrasound imaging. Color Doppler ultrasound red and blue refer to the direction of blood flow, with red blood flow representing the direction of blood flow toward the probe and blue representing the direction of blood flow away from the probe. Color ultrasound blood flow direction is differentiated by the zero base line, which shows blood flow toward the probe above the zero base line and blood flow away from the probe below the zero base line. Color coding indicates the direction of blood flow, with red or yellow chromatograms indicating flow toward the probe and blue or blue-green chromatograms indicating flow away from the probe. Color Doppler ultrasound is suitable for ultrasound examination of all parts of the body and organs, especially for the diagnosis of heart, limbs, blood vessels and superficial organs, abdomen and pelvis.