Doppler Ultrasound Uses Confusing Color Scheme

In my algebra-based General Physics courses, I get many Biology/Pre-med/Life Science majors, so of course many of the examples that I choose tend to be related to those areas. When we cover traveling waves and Doppler effect, I dive into medical diagnostics to show a few of the applications of Doppler effect in that area. Interestingly enough, in Doppler Ultrasound, the color scheme that they use tend to be a bit confusing with what we use in physics. In the Doppler effect, when the source of a.