Because there are so, so many cats and no Clans to separate them into, keeping track of who’s who and who has what rank can be difficult. Luckily, the cats here have formed a plan.

Leaders have ‘crowns’  

These include anything circular or partially circular that fit on the head. It doesn’t matter what it is made of, and often leaders make it their own. 

Leaders who wish to give advice or conduct ceremonies, they will wear a fully circular crown. If they wish to be left alone but still want to be recognized as a leader, they will wear an open crown.

Examples:

Alderstar has a bramble/briar crown with long, sharp thorns (poking mainly outward). 

yes this is a Christ crown on Google

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Blackstar has a crown made of holly berries and leaves (though because  this is the DF, they are mostly rotting).

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Tanglestar has a crown made of thin, twisting twigs with small leaves.

like this, but half-circular

Medicine Cats have herbs 

They may simply choose to have certain leaves or flowers stick from their fur, or they may have necklaces made of vines (to hold it together) and herbs. 

Medicine cats with necklaces are typically more sought after, as they can carry some herbs in them.

Myrtlewing uses thorns as a necklace (he mixes the tail he took in it), though carries herbs as well as poisons in his neckerchief. 

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Stoatspeck colours his coat with anything white, as he likes standing out.

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Shiverrose has purple herbs along her back.

Daycare workers have mushrooms

Like medicine cats, they use ‘necklaces,’ unlike them they only have one thing connected to the vines: a glowing mushroom. The mushroom not only symbolizes that they work at the daycare, but also shows their rank.

Yellow symbolizes the leader of the area (Fungichomp),

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orange symbolizes secondary leaders

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blue symbolizes volunteers and new workers.

Last idea comes from @elementaldeityoffood

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Yes making the crowns and necklaces are tough because of their paws, but with time, they manage it!

After he accepted his fate, Omenstar began helping new leaders by making crowns for them.  Ferntuft begrudgingly (not really, he actually enjoys the work) helps make necklaces because he's particularly handy with his paws