They are complex combinations of multiple bands. The GOES-16 satellite has 6 (or 7, depending if you count shortwave ir) visible bands. Three are used for the red, green, and blue channels to get the "true color" image. Portions of other bands are used in combination with transparency to seamlessly combine the bands that show features the best. At night the IR bands are used in different combinations.
The short version: daytime imagery is derived from GOES-16's red, blue, and near-IR (band 3) channels, with a simulated green channel. Night imagery's all IR; the base map (with city lights) is static and derives from a different satellite.
If you've never heard of it, this bird always stays on the sunlit side of the planet and takes true color images
Goes-17 sees at best 2x2 km boxes (igfov depends on wavelength) and uses mirrors on servos to quickly scan the disk. DSCOVR is simply far enought away that it can see the full disk.
If you need reference materials for how earth like planets look from space, use DSCOVR images, everything else is fake!
And, as a curious artist— is the 'GeoColor' image composited by the satellite camera or done manually afterward in post? Mostly, I'd love to see raw stills of the different bands they reference in the image (like the infrared band).