Quote from Prime_Jetspace
Whoa. In the jar, Assets > Minecraft has a Shaders folder, along with everything else a resource pack changes (excluding sounds, of course). However, I doubt the they change shaders yet, because the folder contains .json files, not .mcmeta.
I'm pretty sure you can change shaders in resource packs. I changed a random number in one of the json files in a resource pack, and my shaders went all wierd.