The Slime Mold Color Guide: Identifying Your Blob

When you find a slime mold in the wild, the first thing you notice isn’t its scientific name—it’s its color. From neon yellow to deep chocolate brown, these colors are the biological “uniforms” of different species.

Here is your quick-reference color guide.

🟡 The Yellows (The Superstars)

The most common color for the active

plasmodium: The moving, feeding stage of a slime mold.

.

• The Species: Likely Physarum polycephalum (bright, lemon yellow) or Fuligo septica (foamy, paler yellow).
• The Meaning: This is the “Full Speed” stage. The blob is active, hungry, and exploring.
• Variation: If it turns a pale, crusty yellow, it is starting to become a

  sclerotium: A hardened, dormant 'shield' state.

  to survive the cold or dry air.

⚪ The Whites (The Ghosts)

White slime molds often go unnoticed because they blend in with wood or fungus.

• The Species: Likely Didymium or Physarum album.
• The Meaning: If the slime is “veiny” and moving, it’s a living species. However, if you see white “ghost tubes” that don’t move, these are actually the empty slime trails left behind by a yellow blob that has moved elsewhere.

🔴 The Pinks & Reds (The Rare Gems)

These are the favorites of collectors and photographers.

• The Species: Most famously Lycogala epidendrum (Wolf’s Milk). They look like small pink balls or “bubbles” on logs.
• The Meaning: These species don’t form wide networks like Physarum. If you see a vibrant red web, it might be the rare Physarum roseum.
• Trivia: Lycogala balls “bleed” a milky pink liquid if they are young and punctured.

🟤 The Chocolates & Purples (The Elders)

When a blob is ready to have children, it changes its look entirely.

• The Species: Likely Stemonitis (Chocolate Tube Slime).
• The Meaning: This is the Reproductive Stage. The blob has stopped moving and is turning into spores.
• The Look: They look like tiny, fuzzy hair-like structures or chocolate-colored feathers. If you touch them, they will release a cloud of dark dust.

⚫ The Blacks (The Spores)

Black is almost always the color of Resting Spores.

• The Meaning: The life of the blob (as a single cell) is over. It has converted its entire body into a dry, black powder. These spores can travel on the wind for miles to land somewhere new and start the cycle over again.

Identification Tip: If you want to identify a species for certain, you often need to wait for it to turn its “final” color (brown or black) so you can look at the shape of its spores under a microscope.

Want to see all these in one place? See our Master Species Directory.