As the first post states, the mats are $99 incl freight with just a standard Nissan badge, or no badging at all.
The discount is, your not paying for freight, it's included in the standard price.
The $129 includes custom badging that I have had designed by an embroiderer, there is 3 badges, one on each of the front mats, and one on the centre rear, as you can see in the pics in the first post.
As for colour which shows up dirt the least, mmmm not sure about that one, I would think grey or charcoal possibly, and if you have grey carpet, they would probably suit the interior the best.