You will need to be in debug mode to access the things needed to add a palette. Add this to your library/config.php
$config['debug'] = 'true';
Then you can now see this on the color palette page, these are default for the Master Style but I suggest making your own and make sure to group them together. Use the default ones for reference. Also make sure you are editing the style you want to add them to, do not use the Master Style.