What I expected to happen.
When opening an imported world to the better together update on a natural texture pack, I expected regular nether brick to remain darker than the red nether brick.

What actually happened.
Both red nether brick and dark default nether brick in the natural texture pack has the same bright red appearance even tho they are clearly mined and named differently. This causes the nether fortress to become bright red and there are no more dark nether brick visible or craftable. It will continue to show as the bright red nether brick that is crafted using nether wart.

To duplicate...
Go into a pre beta world that is uploaded to the new version on the natural texture pack and go into the nether. Find a nether fortress which is now bright red and mine those blocks. Find some netherrack and nether wart. And make some red nether brick. Place both types of bricks down next to each other and observe they look identical even tho they have different names.