Add color to bars for Plotly (#6294)

Co-authored-by: maximlt <[email protected]>

holoviews/plotting/plotly/chart.py

@@ -198,8 +198,7 @@ class BarPlot(BarsMixin, ElementPlot):
     show_legend = param.Boolean(default=True, doc="""
         Whether to show legend for the plot.""")
 
-
-    style_opts = ['visible']
+    style_opts = ['visible', 'color']
 
     selection_display = PlotlyOverlaySelectionDisplay()
 
@@ -282,6 +281,12 @@ def get_data(self, element, ranges, style, **kwargs):
 
         return bars
 
+    def graph_options(self, element, ranges, style, **kwargs):
+        if 'color' in style:
+            style['marker_color'] = style.pop('color')
+        opts = super().graph_options(element, ranges, style, **kwargs)
+        return opts
+
     def init_layout(self, key, element, ranges, **kwargs):
         layout = super().init_layout(key, element, ranges)
         stack_dim = None

holoviews/tests/plotting/plotly/test_barplot.py

@@ -155,3 +155,10 @@ def test_bar_group_stacked(self):
         plot = self._get_plot_state(bars)
         np.testing.assert_equal(set(plot['data'][0]['x']), set(pets))
         np.testing.assert_equal(plot['data'][0]['y'], np.array([8, 7, 6, 7]))
+
+    def test_bar_color(self):
+        data = pd.DataFrame({"A": range(5)})
+        bars = Bars(data).opts(color="gold")
+        fig = self._get_plot_state(bars)
+        data = fig["data"][0]
+        assert data["marker"]["color"] == "gold"