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function my_plugin_admin_scripts($hook) {
    if ( 'settings_page_myplugin' != $hook ) { //set your plugin page
        return;
    }
    wp_enqueue_style( 'wp-color-picker' );
    wp_enqueue_script( 'wp-color-picker-alpha', plugins_url( '/js/wp-color-picker-alpha.min.js',  __FILE__ ), array( 'wp-color-picker' ), '1.0.0', true );
}
add_action( 'admin_enqueue_scripts',  'my_plugin_admin_scripts' );

function my_overlay_callback() {
$options = get_option( 'plugin_settings' );

if( !isset( $options['my_overlay'] ) ) $options['my_overlay'] = 'rgba(0,0,0,0.85)';

echo '<input type="text" class="color-picker" data-alpha="true" data-default-color="rgba(0,0,0,0.85)" name="plugin_settings[my_overlay]" value="' . sanitize_text_field($options['my_overlay']) . '"/>';

}