Change attribute default dropdown value

<?php
// Change 'Choose an option' depending on variation - to help it display on one line on mobile.
// From: https://stackoverflow.com/a/34713246/8605943
add_filter( 'woocommerce_dropdown_variation_attribute_options_args', 'am_change_option_none_text' );
function am_change_option_none_text( $args ) {
    //error_log( 'Dropdown args: ' . var_export( $args, true ) );
    if ( 'pa_size' == $args[ 'attribute' ] ) {
        $args['show_option_none'] = 'Choose size';
    }
    if ( 'pa_colour' == $args[ 'attribute' ] ) {
        $args['show_option_none'] = 'Choose colour';
    }
    return $args;
}