def _assert_is_color(value):
        """
        Assert that the given value is a valid brightness.

        :param value: The value to check.
        """
        if not isinstance(value, tuple) or len(value) != 3:
            raise ValueError("Color must be a RGB tuple.")

        if not all(0 <= x <= 255 for x in value):
            raise ValueError("RGB values of color must be between 0 and 255.")