With the dawn of a blue day the world of Solaris is tinted in a deadly blue light. The spectrum of the blue sun is probably rich of ultra violet and gamma radiation. Man can only survive by hiding from those powerful rays. Think of staring into a welding flame. Lem says that the blue sunlight makes all things appear white and that the blinds of the Solaris station close immediately after sunrise.

a blinding blue sun over Solaris