There are plenty of slime colors, and yet, no one has recorded their properties even generally.

Biome

Green, Forest

Alternative names/forms: Meadow

  • Power: ●○○○○
  • Flexibility: ●●●●●
  • Accessibility: +●●●●
  • Essences: Life, Dream, Harmony, Realm

One of the most common colors, and one of the weakest. However, the specific Essence isn't just Life; green slimes also carry a massive amount of Dream, Harmony and Realm essence to balance, leaving them with a surprising amount of weird uses.

Light Blue, Sky

  • Power: ●●○○○
  • Flexibility: ●●●○○
  • Accessibility: ●●●●●
  • Essences: Flow, Breath, Spark, Form

Usually considered second common. It's stronger than green, but not by much, and having four whole normal Essences all in almost equal amounts leaves blue with very few interesting uses. On the other hand, its inherent desire to mix with things, strong even by slime standards, leaves it with the few uses that are genuinely useful.
The most common source of sky slimes is slime islands - massive overgrown slimes lazily flying around blown by the wind, dropping slimes in different states of being killed by gravity.

Dark Blue, Sea

  • Power: ●●○○○
  • Flexibility: ●○○○○
  • Accessibility: ●●●●○
  • Essences: Flow, Breath, Veil

Technically the most common slime color. However, sea slimes are nearly indistinguishable from sea water, and mostly eat algae. Their cores are generally oversized and not all that powerful, and the slime is basically just slightly weird sea water.

Dark Orange, Magma

  • Power: ●●●○○
  • Flexibility: ●●●●○
  • Accessibility: ●●●○○
  • Essences: Aura, Form, Spark

While they look like blobs of magma rolling around, they are a lot less dangerous. Their temperature is nowhere near high enough to seriously damage metallic weapons, and their attacks are only as dangerous as those of blue slimes, just done in fire burns and not chemical ones. Their cores and slime have a lot of uses, largely related to fire, stone and smithing - although it does have some uses in potion making as well.
While they are very common in their usual element, their usual element is near volcanoes. Protip: if you can do it with one magical way or another, you can easily kill them with snowballs.

Light Orange, Fire

  • Power: ●●●●○
  • Flexibility: ●●●○○
  • Accessibility: ●●○○○
  • Essences: Breath, Form

Magma slime's more fiery cousin. Their cores have less uses, being nearly pure fire, but a lot more power. The most common source is similar to sky slimes - slime islands - but these islands are always in a place that's extremely hot, like an active volcano, and too hot to be survivable for normal humans.

Gem

  • Power: ●●●○○
  • Flexibility: ●●●●○
  • Accessibility: ●●○○○
  • Essences: Flow, Crystal, Spark, Dream

These rare and misleadingly named cave slimes are actually made of highly mineralized water. Their cores are highly magically flexible, but have very few uses in smithing, and the slimes are extremely hard to see without a strong light.

Essence

Essence slimes are fairly rare even in their home world (how often have you seen a Life slime?).

Life

  • Power: ●●●○○
  • Flexibility: ●●○○○
  • Essences: Life, Spark, Veil

These not-terribly-common slimes almost look like a real animal and not just what the slimes are.

Flow

  • Power: ●●●●○
  • Flexibility: ●●●●○
  • Essences: Flow, Dream, Harmony

These slimes cannot stand in the same place, always moving, always changing. Always drumming.

Crystal

  • Power: ●●●●○
  • Flexibility: ●●○○○
  • Essences: Crystal, Breath, Spark

These slimes look more like big shining crystals than the usual blobs. They have a tendency to release a lot of energy to defend themselves, too, although they aren't particularly durable and will often fall apart after a good hit.

Form

  • Power: ●●●●●
  • Flexibility: ●○○○○
  • Essences: Form, Dream, Aura

If you see a dark green cubic block of stone sitting in a weird place, run. Just run. They are dangerous to be near even if they don't know you're there, and will absolutely kill you through any armor if they do; and they're even more durable than they look.

Realm

  • Power: ●●●○○
  • Flexibility: ●●●○○
  • Essences: Realm, Light, Breath

While not particularly interesting on their own, they're unique in that they can be occasionally seen in the World of Realm, floating between the pieces of the World of Life.

Veil

  • Power: ●●●○○
  • Flexibility: ●●●●○
  • Essences: Veil, Aura, Life

These pitch-black blobs are almost universally the only native thing moving in the World of Veil.

Harmony

  • Power: ●●○○○
  • Flexibility: ●●●○○
  • Essences: Harmony, Light, Flow

You will more likely hear them than see them first; they look more like shining, noisy balls than slimes. They can pass through solid objects and aren't affected by gravity.

Spark

  • Power: ●●●●○
  • Flexibility: ●●●○○
  • Essences: Spark, Life, Crystal

These slimes look more mechanical than alive. Their bodies are made of a mix of slime-based alloys.

Dream

  • Power: ●●●●○
  • Flexibility: +●●●●
  • Essences: Dream, Flow, Form

Form lets them stay real and causing Dream havoc for a lot longer than seems possible. Which is part of the point.

Breath

  • Power: ●●●●○
  • Flexibility: ●●○○○
  • Essences: Breath, Crystal, Realm

These slimes are more likely to grow into large, ground-covering, bush-like shapes than stay blobs.

Aura

  • Power: +●●●●
  • Flexibility: ●●○○○
  • Essences: Aura, Form, Veil

Where Form slimes are a lethally dangerous brick, these are a lethally dangerous catapult, able to fry living things alive from a distance. Thankfully, their vision is a lot worse than their attack range.

Light

  • Power: ●●●○○
  • Flexibility: ●●○○○
  • Essences: Light, Harmony, Realm

These are similar to Harmony slimes, except they glow much stronger, and can teleport.

Slime hats

Slimes can occasionally carry non-slime elements around. These "hats", as locals call them, are not what they seem like: while they will generally have the appearance of a part of nature native to the slime, what they are are an assimilated item, which will quickly become fully slime.
Most often, this is seen with forest slimes, which carry around ferns on top. These hats are generally too small to be of much use, but they can be used as tool handles, in which case they behave very similarly to the slimewood composite. Occasionally, an overgrown forest slime can carry around an entire tree as a hat, which is entirely made of slimewood.
Most slime types can carry around plants or trees, so there's little point in writing out every type. The slime will inevitably turn the plant into a fern tree, no matter what plant it was. Most of them behave like slimewood, except for a couple volcanic slime types, where the trunk is made of compressed slimes of a type.

Other slime hats include:

  • Fish
  • Crystals and nuggets of slime composites
  • Tools
  • Humans