Different Mineshaft Wood Type Below Y=0

I have a pretty simple suggestion to make mineshafts look a bit better. I've noticed the bright color of oak wood doesn't blend very well with the new grimstone block. It makes mineshafts below Y=0 feel a little out of place. So, why not replace oak wood with a different type, such as spruce or dark oak wood? I believe this would make mineshafts fit in with the gloomy theme of the depths of the world much better.