Stonecutter blade changes colour when you put certain blocks next to it.

On Minecraft, when you place a cartography table on the left of a stonecutter, the stonecutter's blade turns black. 

I then found out that when you put a block that is not a cartography table next to the stonecutter and when you place a block on the other side of the stonecutter, is blade turns white. 

When you put a block that is not a cartography table on all sides of the stonecutter, its blade turns an even brighter white. 

How to reproduce:

1. Place a stonecutter.
2. Place 1 block of planks on the left of the stonecutter. 
3. Place the cartography table on the right of the stonecutter. You can also place the cartography table on the left of the stonecutter instead of the planks. 

Expected results: The stonecutter stays the same. 

Observed results: The stonecutter's blade turns black. 

     4.  Destroy the blocks surrounding the already existing stonecutter. 

     5.  Place 2 blocks that are not cartography tables on the left and right of the stonecutter. 

Expected results: The stonecutter's blade stays the same. 

Observed results: It turns white. 

    6.  Place a block behind and in front of the stonecutter. 

Expected results: The stonecutter's blade turns an even brighter white.