There are lots of cats. Here's a way I've made to keep track of them all! But watch out! It is updated to the latest chapter, so it might contain spoilers!

HollowClan

Leader

Woodstar - Tan tom with leaf-green eyes; father of Sprucekit and Lilykit

Deputy

Oakleaf - Light tan tom with amber eyes and a cream muzzle

Medicine Cat

Birchmuzzle - Cream she-cat with a light and dark brown tail and white muzzle

Warriors

Daisypatch - Very light tan she-cat with a white hindpaw (left) and muzzle

Pineheart - Dark brown tom with dazzling blue eyes and a light cream chest
Apprentice - Nightpaw - Jet black she-cat with golden yellow eyes

Dappletrunk - Dark tan she-cat with brown dapples and blue eyes

Thornbush - Tan tom with green eyes

Snowmelt - Long-haired white she-cat with shimmering golden eyes

Stonepath - Gray tabby tom with blue eyes shading from age
Apprentice - Starpaw

Shadowtail - Black tabby tom with amber eyes
Apprentice - Grasspaw

Pineneedle - Dark brown tabby tom with a large cream spot on his shoulder; twin of Bramblestripe
Apprentice - Falconpaw

Bramblestripe - Dark brown tabby tom with a large cream spot on his shoulder; twin of Pineneedle
Apprentice - Chippaw

Whitetiger - White she-cat with chocolate brown tabby stripes

Apprentices

Groundpaw - Dirt-brown tom with a paw-shaped print on his shoulder

Nightpaw - Jet black she-cat with golden yellow eyes

Starpaw - White she-cat with fading brown from paws to her belly fur

Falconpaw - Brown tom with feather-like fur

Chippaw - Very dark brown tom with regular brown paws and a chipped ear

Queens

Dovecall - Gray she-cat with fading white fur from her paws to her belly fur; mother of Starpaw, still waiting for next litter

Barebush - Brown tabby she-cat with beautiful silver eyes

Orangestream - Ginger she-cat with white paws and dapples up her legs; mother of Treekit, Gingerkit, and Aquakit

Barkpool - Wood-colored she-cat with water-blue eyes; mother of Sprucekit and Lilykit

Elders

Hailcloud - White tom with gray stripe across the top of his muzzle

Raindapple - Gray-white she-cat with small gray dapples that makes her look like she walked through light rain

Kits

Treekit - Dark brown tabby tom with dazzling green eyes

Gingerkit - Ginger tabby she-kit with blue eyes

Aquakit - White she-kit with ginger tabby stripes and dapples and eyes like pools

Sprucekit - Large, sleek dark brown tabby tom with green eyes and broad shoulders

Lilykit - Small light cream she-kit with blue eyes and slightly darker tabby stripes

Dawnkit - White she-kit with ginger fur on her paws and legs and silver-blue

Spotkit - Gray tom with spots all over his body and silver eyes

BarkClan

Leader

Rushstar - Brown tom with a ginger muzzle and a long gray tail
Apprentice - Rabbitpaw

Deputy

Forestgrowth - Brown tom with constantly damp fur like soil

Medicine Cat

Poppyseed - Cream she-cat

Warriors

Freezepool - White she-cat with elegant blue eyes and gray dapples up her legs

Ravenfeather - Black she-cat with with a ginger tail-tip and amber eyes
Apprentice - Featherpaw

Riverbank - Brown she-cat with white paws and dapples up her legs and black fur on her forehead
Apprentice - Icepaw

Icywind - White tabby she-cat with gray paws and blue eyes
Apprentice - Harepaw

Snakefang - White tom with ginger paws and a black tail-tip

Downpelt - Blue-gray she-cat with a pelt like the down of a bird
Apprentice - Softpaw

Owlwing - Brown tom with a white chest and paws

Apprentices

Rabbitpaw - Tan she-cat with a white flank, tail, and left hindpaw

Harepaw - Tan tom with a black flank and left hindpaw and a light gray tail

Icepaw - Blue-gray she-cat with blue eyes

Softpaw - Light cream she-cat with white patches and soft fur

Featherpaw - White tabby she-cat with thin gray tail

Queens

Lightfeather - White she-cat with gray tabby stripes and a ginger muzzle

Longleg - Silver she-cat with ginger muzzle and right hindpaw and long legs

Elders

Shiverwind - Graytabby tabby tom with a ginger patch on his left eye

Jayflight - Blue-gray tom with a white tail and underbelly

Kits

Firekit - Ginger tom with amber eyes

Flamekit - Ginger tom with orange eyes

Dovekit - Gray she-kit with white tabby stripes and a dark gray tail

RootClan

Leader

Fishstar - Ginger she-cat with blue-green eyes

Deputy

Coldwind - Gray tom with icy blue eyes

Medicine Cat

Fluffypelt - White she-cat with very fluffy fur
Apprentice - Dawnpaw

Warriors

Lightfoot - Ginger she-cat with white paws and green eyes

Snowyground - Black tom with snowy white paws and gray eyes
Apprentice - Darkpaw

Quickshadow - Black tom with golden eyes and long legs
Apprentice - Riverpaw

Pondripple - Muscular white tom with blue eyes and usually ruffled fur
Apprentice - Paddlepaw

Pebblebank - Gray tom with a white spot over left eye

Apprentices

Darkpaw - Black she-cat with white dappled ears and golden eyes

Riverpaw - Brown she-cat with black dappled ears and golden eyes

Paddlepaw - Jet black she-cat with blue eyes

Dawnpaw - Gray tabby she-cat with darker gray muzzle and tail-tip

Queen

Watershine - Blue-gray she-cat with blue eyes

Goldenheart - Light ginger (strangely yellow) she-cat with white dappled ears and golden eyes

Elders

Stormsky - Gray tom with light gray eyes

Kits

Weatherkit - Light gray she-kit

Branchkit - Light brown tom

LeafClan

Leader

Bushstar - Tortoiseshell tom with green eyes

Deputy

Birdsong - Black she-cat with green eyes

Medicine Cat

Daisyshadow - White she-cat with gray paws and yellow eyes

Warriors

Foxflight - Ginger she-cat with black paws and white stomach and amber eyes
Apprentice - Clawpaw

Thunderclash - Gray she-cat with black spots and kind blue eyes

Pebbleshift - Blue-gray tom with golden eyes
Apprentice - Spottedpaw

Rockyland - Gray tabby tom with brown eyes

Apprentices

Clawpaw - Brown tabby tom with blue eyes; born from kittypets Paige and Harold

Spottedpaw - Tortoiseshell she-cat with unusual gray eyes

Queens

Flowerberry - White she-cat with a tan spot over her eye (left) and brown spot on hindpaw (right); mother of Yellowkit and Shellkit

Elders

Katie - Brown she-cat; kittypet born

Kits

Yellowkit - Ginger tom with yellow eyes; bigger brother of Shellkit

Shellkit - Tortoiseshell she-kit with blue (left) and yellow (right) eyes; little sister of Yellowkit

Glowkit - White she-kit with blue-silver eyes; orphan

Animals outside Clans

Paige - Light brown she-cat with blue eyes that lives in the barn; mother of Clawpaw

Harold - Brown tabby tom with yellow eyes that lives in the barn; father of Clawpaw

Cookie - Fox that lives in the Cave of Terror; finds communication between it and two cats (no spoilers)

That is all of the cats so far. Enjoy~