add_filter( 'woocommerce_rest_prepare_product_object', 'custom_change_product_response', 20, 3 );
add_filter( 'woocommerce_rest_prepare_product_variation_object', 'custom_change_product_response', 20, 3 );

function custom_change_product_response( $response, $object, $request ) {
 $variations    = $response->data['variations'];
 $variations_res   = array();
        $variations_array = array();
        $var              = array();
        if ( ! empty( $variations ) && is_array( $variations ) ) {
            foreach ( $variations as $variation ) {
                $variation_id                    = $variation;
                $variation                       = new WC_Product_Variation( $variation_id );
                $variation_attributes            = $variation->get_variation_attributes();
                $variations_res['variation_id']  = $variation_id;
                $variations_res['on_sale']       = $variation->is_on_sale();
                $variations_res['regular_price'] = (float) $variation->regular_price;
                $variations_res['sale_price']    = (float) $variation->sale_price;
                $variations_res['currency']      = get_woocommerce_currency_symbol();
                $variations_res['sku']           = $variation->get_sku();
                $variations_res['description']   = $variation->get_description();
                $variations_res['quantity']      = $variation->get_stock_quantity();
                if ( $variations_res['quantity'] == null ) {
                    $variations_res['quantity'] = '';
                }
                $variations_res['in_stock']        = $variation->is_in_stock();
                $featured_image                    = wp_get_attachment_image_src( get_post_thumbnail_id( $variation_id ), 'shop_catalog' );
                $variations_res['variation_image'] = $featured_image[0];
                if ( $variations_res['variation_image'] == null ) {
                    $variations_res['variation_image'] = " ";
                }
                foreach ( $variation_attributes as $key => $value ) {
                    if ( $key == 'attribute_pa_color' ) {
                        $variation_attributes[ $key ] = get_color_code_by_name( $value );
                    }
                }
                $variations_res['variation_attributes'] = $variation_attributes;
                $variations_array[]                     = $variations_res;
            }
        }
        $response['product_variations'] = $variations_array;
}
return $response;
}