Sandy desert appears light blue in the Snow RGB images, in some areas with greenish shades. More greenish shades appear at lower solar elevations. Rocky desert appears medium blue (see the images below and left).
Meteosat, SEVIRI Snow RGB for 27 December 2014, 12:00 UTC
Explanation of the colours for sandy desert (see the recipe):
• The reflectivity of sand is higher in the NIR1.6 channel than in the VIS0.8 channel. After linear stretching, the green signal will be even higher compared to the red beam (see the ranges in the recipe). For high solar elevation usually both, the green and the blue components saturate, while the red component is also considerably high. The resulting colour will be light blue. If the solar elevation is lower, then the sandy desert is shown in greenish tones in some areas.