def _darkest(self):
rgb, n = (<NUM_LIT:1.0>, <NUM_LIT:1.0>, <NUM_LIT:1.0>), <NUM_LIT><EOL>for r,g,b in self:<EOL><INDENT>if r+g+b < n:<EOL><INDENT>rgb, n = (r,g,b), r+g+b<EOL><DEDENT><DEDENT>return rgb<EOL>
Returns the darkest swatch.

        Knowing the contract between a light and a dark swatch
        can help us decide how to display readable typography.