Just for future reference, this has been added in v5.3.6.
At bottom of page here:
https://www.advancedcustomfields.com/resources/adding-custom-javascript-fields/
acf.add_filter('color_picker_args', function( args, $field ){
// do something to args
args.palettes = ['#5ee8bf', '#2f353e', '#f55e4f']
// return
return args;
});