Its the colour of the laser used to read the disk Growler. Standard DVD and CD players use a red beam.
Really? How mind bogglin' is THAT then!? 
My life is hereby changed forever. 
Before I nod off with all this excitement like, can you very very briefly explain why that is so important, if indeed it's important at all in fact...to you techno 'eds that is, not this cave man.
Well, as you ask Growler...
A normal DVD has a red laser with a wavelength of 650nm. The technology has reached a point where the wavelength of light is th limiting factor on how close you can put the tracks on the disc!
A Blu-Ray player uses a blue-violet laser with a wavelength of 'only' 450nm... It allws the 'tracks' on the disc to be placed closer together and hence each disc can hold more data. A Blu-Ray disc can hold five times as much data as a standard DVD...
Okay...?
