Looking from inside a ship, through a window, white or blue lines in black space are seen when a ship is traveling through Hyperspace.
However, from the outside, a blue, cloudy tunnel is seen.
Is there an explained reason for this?
The stretching stars is only seen just as a ship enters and exits hyperspace, showing the ship's acceleration/deceleration. However, once lightspeed is achieved, all that can be seen is the cloudy blue hyperspace tunnel (whether inside the ship or not).
Entering hyperspace (as seen in the third Star Wars: The Force Awakens trailer):
Exiting hyperspace (as seen in Return of the Jedi):