To add to the redux docs.

new-presets-merge-example.php

 array('id' => 'dovytest', 'type'=>'typography', 'title' => 'Dovy Test'
            ),
            array(
                'id'       => 'opt-presets',
                'type'     => 'image_select',
                'presets'  => true,
                'title'    => __('Preset', 'redux-framework-demo'),
                'subtitle' => __('This allows you to set a json string or array to override multiple preferences in your theme.', 'redux-framework-demo'),
                'default'  => 0,
                'desc'     => __('This allows you to set a json string or array to override multiple preferences in your theme.', 'redux-framework-demo'),
                'options'  => array(
                    // Array of preset options
                    '1'      => array(
                        'alt'   => 'Preset 1',
                        'img'   => 'http://avada.dev/wp-content/themes/avada3.8/assets/images/patterns/header1.jpg',
                        'presets'   => array(
                            'dovytest'     => array(
                                'color' => '#000000',
                            )
                        ),
                        'merge' => 1
                    ),
                    // JSON string of preset options
                    '2'       => array(
                        'alt'     => 'Preset 2',
                        'img'     => 'http://avada.dev/wp-content/themes/avada3.8/assets/images/patterns/header2.jpg',
                        'presets'   => array(
                            'dovytest'     => array(
                                'color' => '#f8f8f8',
                            )
                        ),
                        'merge' => array('dovytest')
                    ),
                ),
            ),