diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
index 6102fd3d3ed3..3ff77f1308b5 100644
--- a/lib/matplotlib/axes/_axes.py
+++ b/lib/matplotlib/axes/_axes.py
@@ -3288,6 +3288,20 @@ def grouped_bar(self, heights, *, positions=None, group_spacing=1.5, bar_spacing
            boxplot(values, positions=..., tick_labels=...)
 
         """
+        # grouped_bar() controls the label and color of each dataset's bars via the
+        # dedicated *labels* and *colors* parameters, and passes them positionally to
+        # bar(). A 'label' or 'color' in kwargs would therefore be passed to bar()
+        # twice, raising an opaque "multiple values for keyword argument" TypeError.
+        # Reject them early with an actionable message pointing to the plural
+        # parameters (see #30739).
+        for kwarg, alternative in [("color", "colors"), ("label", "labels")]:
+            if kwarg in kwargs:
+                raise TypeError(
+                    f"grouped_bar() got an unexpected keyword argument '{kwarg}'. "
+                    f"grouped_bar() sets the {kwarg} of each dataset's bars "
+                    f"internally; use '{alternative}' to control the per-dataset "
+                    f"{kwarg}s.")
+
         if cbook._is_pandas_dataframe(heights):
             if labels is None:
                 labels = heights.columns.tolist()
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
index 3189076c7655..84f30258e1ac 100644
--- a/lib/matplotlib/tests/test_axes.py
+++ b/lib/matplotlib/tests/test_axes.py
@@ -2315,6 +2315,20 @@ def test_grouped_bar_hatch_sequence():
             assert rect.get_hatch() == hatch
 
 
+@pytest.mark.parametrize("kwarg, alternative", [("label", "labels"),
+                                                ("color", "colors")])
+def test_grouped_bar_reject_singular_label_color(kwarg, alternative):
+    # grouped_bar() passes the per-dataset label/color to bar() itself, so a
+    # 'label' or 'color' in kwargs would be passed twice and raise an opaque
+    # "multiple values for keyword argument" TypeError. It should instead fail
+    # early with a message pointing to the plural parameter. See #30739.
+    fig, ax = plt.subplots()
+    heights = [np.array([1, 2]), np.array([2, 3])]
+    with pytest.raises(TypeError, match=f"unexpected keyword argument '{kwarg}'.*"
+                                        f"use '{alternative}'"):
+        ax.grouped_bar(heights, **{kwarg: "dataset"})
+
+
 def test_boxplot_dates_pandas(pd):
     # smoke test for boxplot and dates in pandas
     data = np.random.rand(5, 2)