Well, they show pretty good in the image you linked to, so I'm not sure what the difficulty is. (Unless you maybe thing this is a B&W pic of a color tartan!) :-)

The main color is a dark, marled grey. The secondary color is a lighter mid-grey. Then the overstriped are black and a very pale grey that almost looks like it has a shade pink to it.

Here's a picture of the tartan in action: