what the colors on a weather radar mean
Radar images are color-coded to indicate precipitation intensity. The scale below is used on the USATODAY.com images. The light blue color is the lightest precipitation and the purple and white are the heaviest. Sometimes radar images indicate virga, or precipitation that isn't reaching the ground. Reflectivity not only depends on precipitation intensity, but also the type of precipitation.
Approximate Rainfall Rates. The Bureau's radar images show the location of rain in relation to local features such as the coastline, with different colours used to depict rainfall intensity. For example off-white represents light drizzle, while dark red is used to depict very heavy rain (possibly containing hailstones).