The NASA Earth Observatory has just posted a very powerful false-color image of the flooding that resulted from opening the Morganza spillway last week.
The reason for the false-color in this imagery is to more easily highlight the flooded areas. Specifically:
The false-color images combine infrared, red, and green wavelengths to help distinguish between water and land. Clear water is blue, and sediment-laden water is a dull blue-gray. Vegetation is red; the brighter the red, the more robust the vegetation. Gray patches away from the center of the floodway are likely farm fields that have recently been burned or cleared.