Wither Skeleton spawned with grimey sword

Washing of Dirt

Washing of Dirt in water causes it to dissolve immersively. Depending on the type of dirt it might clean faster like dirt and dust or take longer like ink or burn marks.

Procedual Blood and Dirt

These armors and weapons have the same amount of blood on them but look different. Each piece of gear has its own seed.

Natural Loot Table

Natural loot tables can have dirty tools, armor or food depending on where they are. A chests in a Dessert-Biome might have sand on the food.

Natural Mobs with dirty Armow and Weapons

Mobs can spawn with dirty armor and tools, also depending on biome

Mining is messy

Expect to get dirty when you are surrounded by stone, sand, etc.

Bloodpool size depends on damage dealt

More damage means bigger pool of blood

Different mobs have different blood colors

Footsteps after stepping in blood

Stepping in blood lets (only player as of now) players leave footprints behind for a short while.

Eating dirty food

Is not recommended. But don't worry the 3 second rule will probably be good enough.