code: def test_to_color_strings(colors):
      """Tests for function to_color_strings with different color inputs."""
      if len(colors) == 3:
          expected = ["#0000ff", "#ff0000", "#7f7f7f"]
      else:
          expected = ["#ff0000", "#008000", "#000000", "#ffffff"]
      assert to_color_strings(colors) == expected
  
imports: import base64
  import os
  import re
  import tempfile
  import numpy
  import pytest
  from nilearn.datasets import fetch_surf_fsaverage
  from nilearn.plotting.js_plotting_utils import add_js_lib, colorscale, decode, encode, get_html_template, mesh_to_plotly, to_color_strings
  from nilearn.surface import load_surf_mesh
label_desc: Use image node_id 13 for calling a global function with example usage: test_to_color_strings(colors) without return types