The "Blue Marble" photo of Earth taken in 1972 by the crew of Apollo 17 on their way to the Moon.
Short answer: Mostly blue, with some green, brown and white.
Long answer: There are several main colours of the planet Earth, the dominant colour being blue. This comes from the oceans and the atmosphere. Water is blue when it's more than a few metres deep, and the oceans also reflect blue light from the atmosphere. The atmosphere is blue due to a phenomenon called Rayleigh scattering. Together, these give the planet a blue appearance from a long way away in space.
Closer to Earth we can see brown mountains and deserts, with green forests.
White is also common in both ice around the poles and clouds around the planet.
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