Refer to figure.
Weather radar displays use colour coding to represent the reflectivity of precipitation, which is a measure of the intensity of the radar echo returned from hydrometeors (like raindrops, snow, or hail). The colours provide an intuitive way to assess the severity of weather systems at a glance.

The standard colour sequence for increasing precipitation intensity is:

• Green: Light precipitation (e.g., drizzle or light rain)
• Yellow: Moderate precipitation
• Orange: Heavy precipitation
• Red: Very heavy precipitation, possibly indicating severe thunderstorms or hail

In some systems, additional colours like purple or white are used to denote extremely intense echoes.

• "Blue - green - orange - yellow": Blue is not standard in intensity sequences, it’s often used in satellite imagery (e.g. IR or water vapour), not radar reflectivity.
• "Red - orange - yellow - green": Reverses the correct sequence, red indicates the highest intensity, not the lowest.
• "Green - yellow - blue - red": Blue does not represent intensity.