There are many different versions of 3d glasses, from the very cheap, disposable, paper ones that most people think of wearing to watch 3D movies in the 1980’s and 1990’s and special effects in magazines, to the much more sophisticated LCD shutter glassed for 3-D HDTV which are favoured by the likes of Sony and Panasonic for their LCD screens. The reason the LCD glasses are more expensive is that they recieve a signal from the TV set to synchronise with before they alternately darken each side of the glasses so that you actually “see” a series of images through your left and right eyes which your brain stitches together into a 3D image.
The cheaper glasses, with the red side and blue side, don’t use the same effect. Instead, all the information for a 3-D image is contained in the picture itself, which is called an anaglyph. Your eyes “see” two different images because of the differently coloured filters, and the brain interprets the coherent image as 3-D. Relying on colour filters naturally means that the overall colour of the 3D image suffers. Another way to achieve the same effect is to make use a light with different polarity so that when using polarised glasses, the left eye sees an image with one polarity and the right eye sees a different image with different polarity. You brain constructs a 3D image from the two separate images but with no loss of colour.
So which is best? Well, for the purposes of 3D TV and gaming, you’ll probably need a set of LCD shutter glasses as Sony and Panasonic are marketing TV sets requiring those glasses. For the cinema, it will depend on how the movie was filmed, and you may need different glasses for different movies until a standard is agreed, or one format becomes dominant. At the moment, companies like RealD and MasterImage make the polarised glasses, and XpanD make LCD glasses. Dolby also makes their own type of glasses for their 3-D Digital Cinema system!