code: def test_server_on_change_round_trip(
      self, bokeh_server_page: BokehServerPage
  ) -> None:
      colorpicker = ColorPicker(color="red")
      page = bokeh_server_page(mk_modify_doc(colorpicker))
  
      el = find_element_for(page.driver, colorpicker, "input")
  
      # new value
      enter_value_in_color_picker(page.driver, el, "#0000ff")
      page.eval_custom_action()
      results = page.results
      assert results["data"]["val"] == ["#ff0000", "#0000ff"]
  
file_path: bokeh/tests/integration/widgets/test_color_picker.py
imports: from __future__ import annotations
  import pytest
  from bokeh.layouts import column
  from bokeh.models import Circle, ColorPicker, ColumnDataSource, CustomJS, Plot, Range1d
  from tests.support.plugins.project import BokehModelPage, BokehServerPage
  from tests.support.util.selenium import RECORD, find_element_for
label_desc: Use image node_id 4 for calling the Test_ColorPicker obj's underlying member method code with example usage: obj.test_server_on_change_round_trip(bokeh_server_page) without return types