Day / night images: Images are from Meteosat satellite. High and cold clouds appear in whitish and darker grey represents lower clouds. In the wintertime very cold surfaces (e.g. snow, ice) appear also in whitish colors. Visible channel is used in the daytime part of the image and infrared channel at night part. The background will change based on time of day.
Daylight images: Daylight satellite images are from Meteosat satellite. Image is RGB combination of visible and infrared channels. Thin and high cirrus clouds appear bluish, thicker clouds whitish and low clouds yellowish.
Night-time images are bluish. Images are yellowish when the Sun appears lower angle (e.g. in winter and in the mornings).
More information about Satellite images.