looks to be old reclaimed wood, kinda with a rough cut or the color may be original patina. the angled stripes you see were possibly where it was attached to the beams....

I've also seen a version done with wood from pallets - these were free from a local hardware store as the pallets were being thrown out anyway. There was a mention of having to be careful about what treatments the wood may have been subject to (pesticides etc), which is very noteworthy.

Here's the link to where they described the process. I think it looks great.
http://www.bowerpowerblog.com/2010/02/nursery-news-accent-wall/

Thanks!