def write(self, fptr):
        """Write an Colour Specification box to file.
        """
        self._write_validate()
        length = 15 if self.icc_profile is None else 11 + len(self.icc_profile)
        fptr.write(struct.pack('>I4s', length, b'colr'))

        read_buffer = struct.pack('>BBBI',
                                  self.method,
                                  self.precedence,
                                  self.approximation,
                                  self.colorspace)
        fptr.write(read_buffer)
Write an Colour Specification box to file.