Changing the color of the Doppler is very easy. Here are the quick instructions:
From the app, select SETTINGS on the main screen and tap Doppler colors.
To change the color of the Doppleru using the Doppler buttons. Hold 
until display shows a rainbow, select color using 
or 
. Press 
to save.
Please see the Basic Use section in the user manual or the basic use instructions on the bottom of the Doppler for other similar features. In a future update, you will be able to set the color in the app.