custom query using keys of a custom field array

Hello everybody!
Need help here.. I tried and sought a lot of thing, but without success..

I’m using a plugin that creates for each new post a custom field that is filled with an array.

This array contains some important values (like some relationships), and now, I’m trying to make a new WP_Query to filter my post with this information.

Reading the codex, I saw that i can make a custom query using meta_keys:

$query = new WP_Query( array(
   'meta_key' => '_color',
   'meta_value' => 'blue',
   'meta_compare' => '='
 ) );

but if the key and value are inside an array?

This code below is wrong.. any ideas?

$query = new WP_Query( array(
   'meta_key' => '_color',
   'meta_value' => array(
      'meta_key' => 'price',
      'meta_value' =>'5',
   )
   'meta_compare' => '='
 ) );

my custom field (doing the get_post_meta($post->ID, ‘_color ‘) in a print_r):

print_r(get_post_meta($post->ID, '_color'));

Array
(
    [0] => Array
        (
            [_code] => 4860
            [_name] => blue
            [_price] => 5
        )
)

retrieve these values in a loop, after a normal query, isn’t a problem.. I just put these values in a string, and read the array.

in my case, for e.g., my try is to make a query with only the posts that have the key “_price” with the value “5”;

thanks in advance!!