fix placeholder rules

.gitignore

@@ -160,4 +160,7 @@ cython_debug/
 #  and can be added to the global gitignore or merged into this file.  For a more nuclear
 #  option (not recommended) you can uncomment the following to ignore the entire idea folder.
 .idea/
-.DS_Store
+.DS_Store
+
+# Claude Code guidance file
+CLAUDE.md

tailwind_merge/core.py

@@ -206,6 +206,8 @@ def __init__(self):
             ('border_opacity', ['border-opacity-']),
              # Text Opacity
             ('text_opacity', ['text-opacity-']),
+             # Placeholder Color
+            ('placeholder_color', ['placeholder-']),
 
 
             # Box Shadow

tests/test_merge.py

@@ -90,4 +90,31 @@ def test_with_modifiers():
         "hover:text-red-500",
         "hover:text-green-500"
     )
-    assert result == "hover:text-green-500"
+    assert result == "hover:text-green-500"
+
+def test_placeholder_merge():
+    """Test that placeholder colors merge correctly"""
+    twmerge = TailwindMerge()
+    result = twmerge.merge(
+        "placeholder-gray-400",
+        "placeholder-red-500"
+    )
+    assert result == "placeholder-red-500"
+
+def test_dark_placeholder_merge():
+    """Test that dark:placeholder-* variants merge correctly - Issue #6"""
+    twmerge = TailwindMerge()
+    result = twmerge.merge(
+        "dark:placeholder-gray-400",
+        "dark:placeholder-red-500"
+    )
+    assert result == "dark:placeholder-red-500"
+
+def test_multiple_modifier_placeholder_merge():
+    """Test placeholder with multiple modifiers"""
+    twmerge = TailwindMerge()
+    result = twmerge.merge(
+        "hover:dark:placeholder-gray-400",
+        "hover:dark:placeholder-red-500"
+    )
+    assert result == "hover:dark:placeholder-red-500"