MODIS (Terra) Corrected Reflectance (bands 3,6,7)The 3-6-7 composite assigns Bands 3, 6, and 7 to the red, green, and blue components of a digital image. This combination is good for revealing snow and ice because they are very reflective in the visible part of the spectrum, and very absorbent in Bands 6 and 7, which are a part of the spectrum called the short-wave infrared, or SWIR.
Snow and Ice
Since the only visible light used in these images (Band 3) is assigned to red, snow and ice appear bright red. The more ice, the stronger the absorption in the SWIR bands, and the more red the color. Thick ice and snow appear vivid red (or red-orange), while small ice crystals in high-level clouds will appear reddish-orange or peach.
Vegetation
Vegetation is absorbent in Band 3 and Band 7, but reflective in Band 6, and so will appear greenish in this band combination. Bare soil will appear bright cyan in the image since it much more reflective in Band 6 and Band 7 than Band 3.
Water
Liquid water on the ground will be very dark since it absorbs in the red and the SWIR, but small liquid water drops in clouds scatter light equally in both the visible and the SWIR, and will therefore appear white. Sediments in water appear dark red.