Fix snapshot test by resetting colour cycle.

src/textual/widgets/_placeholder.py

@@ -74,6 +74,11 @@ class Placeholder(Static):
 
     variant: Reactive[PlaceholderVariant] = reactive("default")
 
+    @classmethod
+    def reset_color_cycle(cls) -> None:
+        """Reset the placeholder background color cycle."""
+        cls.COLORS = cycle(_PLACEHOLDER_BACKGROUND_COLORS)
+
     def __init__(
         self,
         variant: PlaceholderVariant = "default",

tests/snapshot_tests/test_snapshots.py

@@ -2,6 +2,8 @@ from pathlib import Path
 
 import pytest
 
+from textual.widgets import Placeholder
+
 # These paths should be relative to THIS directory.
 WIDGET_EXAMPLES_DIR = Path("../../docs/examples/widgets")
 LAYOUT_EXAMPLES_DIR = Path("../../docs/examples/guide/layout")
@@ -79,6 +81,7 @@ def test_buttons_render(snap_compare):
 
 def test_placeholder_render(snap_compare):
     # Testing the rendering of the multiple placeholder variants and labels.
+    Placeholder.reset_color_cycle()
     assert snap_compare(WIDGET_EXAMPLES_DIR / "placeholder.py")