1. Outer space contains virtually no gas/dust to scatter light.
Outer space is black.
2. The sky is blue because that's the colour of air (mostly nitrogen), which is not totally colourless. You can see this effect looking at distant (10 km-plus) mountains. They have a blue tinge (caused by the intervening air between you and the mountains) known as atmospheric perspective.
3. If the sky's colour was due reflection from the oceans, then it would be white above Antarctica, which is snowy white.
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