What color is the planet Neptune?

The planet is mostly blue. Which seems appropriate since in ancient Roman mythology Neptune was the god of the sea. While there water on Neptune that isn't what makes it appear blue. Its color comes from traces of methane gas in its atmosphere.

Neptune is a gas giant type planet that is probably most like Uranus. Scientist believe the planet has three layers. First, a hot rocky core that may be up 15 times the size of earth. Next a mantle of water mixed with solidified gases. Finally a crust of solidified or liquid hydrogen and helium that gradually thins out into a gas atmosphere.

The Voyager 2 took this photo of Neptune in 1989 The space craft had traveled 12 years before passing about 4,950 kilometers (3,000 miles) above Neptune's north pole. More recent photographs from the Hubble Space telescope show the planet to be a paler blue color.

Neptune was discovered on September 23, 1846. It was the first planet discovered using mathematical prediction.