// using a predefined style
$output->writeln('<info>... contents ...</>');

// custom style using basic colors
$output->writeln('<fg=green;bg=blue>... contents ...</>');

// custom style using true colors
$output->writeln('<fg=#00ff00;bg=#00f>... contents ...</>');

use Symfony\Component\Console\Color;

$color = new Color('#00ff00', '#00f');
echo $color->apply('... contents ...');

// you can mix basic and true colors
$color = new Color('red', '#00f');

// the third optional argument defines the styles
$color = new Color('#000', '#fff', ['underscore', 'reverse']);