Why are blocks showing pink and black (or purple and black) checkerboard in Minecraft

Pink/purple and black checkerboard is Minecraft's "missing texture" fallback. With Optimum Realism it usually means: the pack didn't fully load, a pack format / version mismatch, or another resource pack is overriding ours from the top of the pack stack.

Still seeing it?

How many blocks are affected?

Those are blocks we haven't textured yet (some recent vanilla additions are still being added pack-by-pack), OR the pack version you downloaded is older than your Minecraft version.

  1. Check your pack version: open /account or the home download section to get the latest release
  2. Re-download the right version for your Minecraft version
  3. Drop into .minecraft/resourcepacks/ and re-enable

Another resource pack is overriding ours, or Optimum Realism didn't finish loading.

  1. Options → Resource Packs
  2. Remove ALL active packs
  3. Restart Minecraft completely (close and relaunch)
  4. Re-add Optimum Realism FIRST — it must be at the top of the active stack

Realms and many servers force their own resource pack which takes priority over yours. The pink/purple blocks come from server-side textures the server is sending. You can't override this without the server owner's permission.

On Bedrock this almost always means a world or realm resource pack is overriding ours. Open the world settings → Resource Packs and reorder so Optimum Realism is at the top of the active list.

Related
Why is the Optimum Realism pack not showing in the resource pack list?Why does Minecraft say "Made for an older version" with Optimum Realism?Why does "ENABLE CONNECTED TEXTURES" appear written on Minecraft blocks?Why isn't Optimum Realism RTX loading on Minecraft Bedrock?

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