ADDED: A bit of comments for a reader

dashboard2/main.py

@@ -53,9 +53,12 @@ app.layout = html.Div(
     ],
     className="m-4",
 )
+
+# Now the color selecion and the slider works for both diagrams
 @app.callback(Output("graph_1", "figure"), Input("color", "value"), Input("range", "value"))
 
 def update_graph_1(color, range):
+    # this filter is used twice. This could be improved
     dff = df[(df['y'] > range[0]) & (df['y'] < range[1])]
     fig = px.histogram(dff, x="y", color_discrete_sequence=[color])
     fig.update_layout()