I'm not sure if this is a valid issue, but it seems customizing materials/fancy.json with a resource pack takes no effect. The same goes for sad.json and common.json.

The attached pack unchangeable-fanciness-1.8.0.mcpack is intended to change the color of the sky to #00FF00 (vivid green) when "Fancy Graphics" is enabled, but on 1.8.0 it changes nothing.