Issue with multi-colored flashing blocks in Minecraft 1.8.1 for PC

My world looks like it is having a blacklight party.

There are blocks everywhere that continuously change neon colors (blue, green, red, yellow, and purple) at random.

I could usually fix this by logging out of my Minecraft account and then logging in again, but now that doesn't fix the problem.

I am using a PC with Windows 7 OS to play Minecraft version 1.8.1.

I have attached an image of what it looks like.

This issue started around new years, and now looks like it is permanent as of last night.

If someone can explain what is happening, why it is happening, and if possible how to fix this issue I would greatly appreciate it.

-Bill H.