The color of the sky appears light blue from Earth due to a phenomenon known as Rayleigh scattering. Rayleigh scattering is the scattering of sunlight by molecules and tiny particles in the Earth's atmosphere. The atmosphere is composed mainly of nitrogen and oxygen molecules, which are much smaller in size compared to the wavelength of visible light.
When sunlight enters the Earth's atmosphere, it encounters these small molecules. The shorter wavelengths of light, such as blue and violet, are scattered more easily in all directions by the molecules in the atmosphere. This scattering is responsible for the blue color of the sky that we observe during the day.
Now, when you view the sky from space, the perspective is different. Astronauts in space are outside the Earth's atmosphere, so they don't experience the scattering of sunlight by the atmosphere's molecules. From space, the sky appears black because there is no scattering of sunlight to create the blue color that we see from the surface. Instead, astronauts see the vastness of space, which appears black because there is very little light to scatter in the vacuum of space.
In summary, the blue color of the sky from Earth is a result of sunlight scattering off the molecules in the atmosphere, while the black color of the sky from space is due to the absence of scattering and the lack of significant light sources in the vacuum.