Given a color object, this function writes a file containing the hexadecimal representation of the colors in the object.
writehex(x, file = "")
a color object.
the name of the file to be written.
The name of the file is returned as the value of the function.
This function converts the given color object to RGB and then writes
hexadecimal strings (of the form
#RRGGBB) representing the colors to
the specified file.