I am getting rainbow-textured blocks on occasion. I will be playing a game of Survival Games with my buddy, and all of a sudden, this happens and it screws me up and I die. It has gotten more extreme, once to the point that every block completely disappeared, causing me to die. Other times stone will turn into a sideways furnace and doors will be made out of obsidian, etc. I was only able to capture the rainbow phenomenon via screenshot. As you can see, it occurs with both a different resource pack and vanilla.