'colour SCHEME: Selects a colour scheme
Residents of both countries that have not adopted the metric
system may also spell this command without a \'u\'.  If using a
colour terminal in interactive mode then output is
automatically coloured to make it more readable.  Use \'off\' to
turn off colour, and no name or \'default\' for the default.'

def command_colour(self, cmd=[]):

    if (len(cmd) > 1):
        raise self.Error('Too    many    colour    schemes')
    c = ((cmd and cmd[0]) or 'default')
    if (c not in self._colours):
        raise self.Error(('No    such    colour    scheme:    ' + c))
    self.colour_scheme = c
    self._out_colour()
