Blue shift and red shift have nothing to do with the speed of light. It's a description of the wavelength of light increasing (red shift) and decreasing (blue shift). That doesn't affect the speed, but it makes the visible light "shift" to the red or the blue end of the spectrum respectively.
Red shift shows us that galaxies are moving away from us very fast, stretching the wavelength as the space expands. It is evidence that the universe is expanding.
As for light slowing down, I've already said that the shifting has nothing to do with that, but light can slow down. It slows down through water, through highly viscous liquids, glass, etc.
Red shift shows us that galaxies are moving away from us very fast, stretching the wavelength as the space expands. It is evidence that the universe is expanding.
As for light slowing down, I've already said that the shifting has nothing to do with that, but light can slow down. It slows down through water, through highly viscous liquids, glass, etc.
