The following code will handle all cases including the stock amount display with your custom texts

add_filter( 'woocommerce_get_availability_text', 'customizing_stock_availability_text', 1, 2);
function customizing_stock_availability_text( $availability, $product ) {
    if ( ! $product->is_in_stock() ) {
        $availability = __( 'Sold Out', 'woocommerce' );
    }
    elseif ( $product->managing_stock() && $product->is_on_backorder( 1 ) )
    {
        $availability = $product->backorders_require_notification() ? __( 'Available on backorder', 'woocommerce' ) : '';
    }
    elseif ( $product->managing_stock() )
    {
        $availability = __( 'Available!', 'woocommerce' );
        $stock_amount = $product->get_stock_quantity();

        switch ( get_option( 'woocommerce_stock_format' ) ) {
            case 'low_amount' :
                if ( $stock_amount <= get_option( 'woocommerce_notify_low_stock_amount' ) ) {
                    /* translators: %s: stock amount */
                    $availability = sprintf( __( 'Only %s Available!', 'woocommerce' ), wc_format_stock_quantity_for_display( $stock_amount, $product ) );
                }
            break;
            case '' :
                /* translators: %s: stock amount */
                $availability = sprintf( __( '%s Serie left each color!', 'woocommerce' ), wc_format_stock_quantity_for_display( $stock_amount, $product ) );
            break;
        }

        if ( $product->backorders_allowed() && $product->backorders_require_notification() ) {
            $availability .= ' ' . __( '(can be backordered)', 'woocommerce' );
        }
    }
    else
    {
        $availability = '';
    }

    return $availability;
}