Happens when breaking a block as all sides (top, sides, and bottom) have different scales of darkening colors. 

How to repeat:
1. Find a block (dirt is a good example)
2. begin to break the block and look at all sides of the block to see that the top and sides have darker color schemes

Also compared to over versions the colors are lighter to a degree and universal for whatever side of the block is being broken unless its dirt or something of the sort where it will not show correct breaking