When an entity is standing on soul sand, or on snow that is more than one layer high, it is rendered too dark.
Items you're holding go black when you walk on soul sand
Player and the item he holds turns blacks
Players turn dark when stepping on soul sand.
Standing on Soul Sand makes the player super dark
Players standing on soulsand are dark.
Light levels in the F3 debug menu aren't accurate when standing on soul sand
Ignited TNT, arrow or trident turns black when it falls on soul sand or snow layers
Silverfish and endermites appear black on soul sand
Entities are rendered too dark when in the ground
Entities riding boats, minecarts or other entities are rendered too dark when their hitbox intersects solid blocks
Entities on honey block are dark