Grey paint is not the main issue for satellites

Why are ships painted grey instead of dark blue on top and grey below to camouflage them from satellites?

Grey blends better at range, while satellites tracking ships usually rely on radar-like ocean reconnaissance rather than simple blue-water photography.

Seas are not simply blue, and grey has long been a practical compromise for visual blending. Photo reconnaissance is also not the main way navies try to track ships across oceans. Ocean-reconnaissance radar satellites and similar systems matter more. Radar signature and sensor behavior can therefore be more important than painting a ship blue.