Stain color different on posts and waiting to stain

We are having a new pergola built from cedar. We live in Albuquerque NM (6000ft elevation) and the pergola will be in full sun. The lumber arrived last week and it has been sanded, posts are in the ground, and the boards cut but not mounted. I have two questions:

The samples I ordered from Armstrong Clark just arrived and the contractor put it on some wood remnants. They look very different on the 2x8s vs the 6x6 posts. Please see photos. What would cause this and are there solutions?

I planned to wait to stain but the contractor really wants to stain before mounting the boards as the pergola will be 11ft tall and there will be 2x6 cross boards notched in making it more challenging. He says the wood is dry enough. It measures around 15% moisture when I take a reading. Should I stick with waiting? I was not home to see how the stain samples went on the wood so not sure how it penetrated.

Thanks -