A very subtle blue, almost a gray. I love the texture ans lighting. Some areas seem a little too perfect, though, as if you went a touch heavy on noise reduction.
The lock seems newer than the rest of the door - would be interesting to see this taken slightly lower so as not to include the lock. I think there would be a completely different feeling.
Don't know about blue (maybe my monitor is not calibrated), but that's a splendid image. I'm not sure what makes it for me. Maybe the depiction of multiple different objects in close proximity, each having its own unique shape, and yet it's obvious they are all interconnected. The more I look at it, the more I find it appealing, with its delicate lighting, and the wood and paint textures. Great job, I tell ya. You should consider making a series of such finds.
What's blue here? The paint maybe? Looks greyish/whtie to me. Awkward composition. The handle right in the center isn't appealing and the lock is too close to the edge.