docs: def _invert(color):
      """
      Returns the inverse (negative) of a color.
      The red, green, and blue values are inverted, while the opacity is left alone.
      """
      col = ColorValue(color)
      c = col.value
      c[0] = 255.0 - c[0]
      c[1] = 255.0 - c[1]
      c[2] = 255.0 - c[2]
      return col