The borders have to be the same size I think, because it's the overlap of colors that will change the size of the borders anyways. Still, I have been looking on the internet for some examples and found out that most use a way thicker border for each color, so perhaps the current effect won't work.

I have to say though, if I would make a 3D glasses shader from scratch, I would probably make 3 layers of the total scene, one layer in red, one in blue and one for example green and change their offset and add them together.

As soon as I get my hands on 3D glasses, I will change the code some more,

Cheers