The concrete may not be stained, it may just be wet. The color of concrete also changes with curing and then eventually with time as well. I wouldn't guess that this concrete has a mixed in or sprinkled on stain, but I really hope that the architect can answer for you!

This is actually an integral color concrete. The color is "bamboo" from QC, who unfortunately is out of business. And the concrete was then acid washed to give it a softer more sandstone like finish.

I'm not sure QC is out of business. I found their website "QCconstructionproducts.com" and called the phone number on it and it is working. (4/22/12)