I was playing around with beacon colors in the new 1.8 snapshot, and when I broke a piece of stained glass, I expected the beacon light to switch back to normal, but instead it glitched back and forth repeatedly between normal color and the stained glass color, even though I had removed the stained glass.

How to trigger the bug
1. Place and activate a beacon
2. Place any color of stained glass over the beacon (I used yellow on one and then blue on another, but in theory any color should work)
3. Break the stained glass