fix getting the color data

hvplot/converter.py

@@ -929,7 +929,11 @@ def _process_symmetric(self, symmetric, clim, check_symmetric_max):
                 return False
 
         elif self._color_dim:
-            data = self.data[self._color_dim]
+            data = (
+                self.data[self._color_dim]
+                if self._color_dim in self.data.columns
+                else self.data.index.get_level_values(self._color_dim)
+            )
         else:
             return
 

hvplot/tests/teststatplots.py

@@ -0,0 +1,24 @@
+import numpy as np
+import pandas as pd
+import xarray as xr
+
+from holoviews import Store
+
+import hvplot.xarray  # noqa: F401
+
+
+def test_violin_from_xarray_with_by_and_color():
+    latitudes = np.linspace(-90, 90, 180)
+    longitudes = np.linspace(-180, 180, 360)
+    times = pd.date_range('2023-01-01', periods=365, freq='D')
+    data = np.random.random((365, 180, 360))
+    da = xr.DataArray(
+        data,
+        coords={'time': times, 'lat': latitudes, 'lon': longitudes},
+        dims=['time', 'lat', 'lon'],
+        name='temperature',
+    )
+    plot = da.hvplot.violin(y='temperature', by='lat', color='lat')
+    assert plot.kdims == ['lat']
+    opts = Store.lookup_options('bokeh', plot, 'style')
+    assert opts.kwargs['violin_fill_color'] == 'lat'