When the textures exceeded 4GB, the four byte pointer to the data in the assets file could not actually access the textures (0xFFFFFFFF - 4294967295 bytes) because it was too far away. Instead of finding an actual texture, it either was reading data that wasn't texture (like animation data, model data, etc) or in the middle of some texture, causing the "skittles" to appear.
Comments
How did this happen?
Unity isnt the only one: its reading the wrong data...
https://drive.google.com/file/d/0B_w_cT4IsnDKOGNxX2p2TmJGcGs/view