Are coloured doppler images of heart coloured? i mean do they use colours liked red,orange to highlight important findings. or are they black n white

They are colored: The colors are indicative of the velocity of the blood flow. You may recall the Doppler effect from yr physics classes where they explained the change in pitch of the sound of a train whistle as it passed you. It is used extensively in astronomy (the "red shift"). Anytime that something is moving and vibrating simultaneously the observer will detect a variable pitch. The machine presents that as a