I've noticed ours has faded a bit. I would never have noticed if I hadn't taken a picture when we bought the house and again last year. The brick is a yellowish tan which goes all the way through and it has surface colors of rust, brown, and white. It's the brown and rust that faded.

I also bought some landscaping block that was a dusty reddish color and it is pink now. I bought it about 10 years ago and I'm pretty sure it is a concrete, not fired brick. They have the color all the way through and when one chips it is darker inside.

The Knob Hill brick has a tan background with some grey, red, and slightly darker brown mixed coloration. It seems like the red and Greys are more faded out and the brick looks mostly tan after fading. Today I went to see another house that was 5 years old and the brick looked like new. I think I'm going to call the manufacturer and ask them if they have had complaints.

Depending on what the compounds providing the color to the clay the bricks are made from, some changes in color with long term UV exposure can occur.