code: def test_invalid_color_str_single_char():
      with pytest.raises(ValueError):
          colors.Color("x")
  
imports: import os
  import pytest
  import vtk
  import pyvista
  from pyvista import colors
  from pyvista.examples.downloads import download_file
  from pyvista.plotting.themes import DarkTheme, Theme, _set_plot_theme_from_env
  from pyvista.plotting.utilities.gl_checks import uses_egl
label_desc: Use image node_id 10 for calling a global function with example usage: test_invalid_color_str_single_char() without return types