WP Query issue for multiple values

Question

You use $args but it isn’t define.

IN your form, you need to add double bracket to make $colours an array.

<INPUT TYPE="checkbox" NAME="colour[]" VALUE="red"> Red<BR>
<INPUT TYPE="checkbox" NAME="colour[]" VALUE="blue"> Blue<BR>

$value){
$colours[]=$value;
}

$meta_query = array('relation' => 'OR');
foreach ($colours as $colour) {
    $meta_query[] = array(
      'key'       => 'colour',
      'value'     => $colour,
      'compare'   => 'like',
    );
}
$args = array('meta_query'=>$meta_query);
$query = new WP_Query($args);