Trying to find the difference between the wood types or colors of concrete isn't as important as trying to find the difference between the different ores. It's a Caves & Cliffs update: Mining was in their main focus, not updating everything so color-blind people can distinguish the different wood types. Plus, I'm pretty sure Mojang didn't think of everything because they had certain other goals in mind.
Distinguishing between iron, redstone, and diamond is much more important than trying to distinguish concrete colors and wood types, IMO.