I think it is common. My Pyrs have always gotten more beige as they age. Just yesterday I was looking for a picture of Kodiak for my cell phone. I was amazed at how pure white and spikey his coat was when he was little. He is two and half now and his coat is beige. My 9-year old boy Fermet's coat was only pure white for about two years and the deep grey markings on his lower back and bum became more apparent as he aged. The other thing is that I always thought the texture of that fur was more course.
I used a whitening shampoo on Fermet one time and I didn't quite follow the directions to the letter and he ended up having a few light blue spots. It made his fur really pretty white but it wasn't worth it.
Christine/Kodiak
From: christinecvs@aol.com
To: pyrnet-l@pyrnet.org
Sent: Thursday, June 17, 2010 9:21:19 AM
Subject: [pyrnet] Pyr getting more colour with age